Seasonal Summary Great Lakes Winter 2023-2024 by the North American Ice Service

The ice coverage this year over the Great Lakes as a black line with all past seasons represented by light blue lines and the historical average as a red line. The black line representing this years’ ice coverage in Figure 1 is significantly below the red line representing the median average years’ ice coverage for almost the entire season giving a visual indication of how much less ice coverage was on the Great Lakes this year than during a normal year. The black line representing this year’s ice coverage is flat with a value of zero for about a month both at the start and at the end of what would be the normal season. The normal or average ice coverage represented by the red curve has positive values during these times shows ice coverage is normally present at these times. This graphically shows how much shorter this ice season was to the average ice season.

The six-month temperature anomaly over the Great Lakes from the start of November 2023 to the end of March 2024 It shows in orange color that the air temperature anomaly averaged between 2 to 2.5°C warmer than normal over the southeastern Great Lakes and in red color that the temperature anomaly averaged 3-4°C warmer than normal over the northwestern Great Lakes between November 2023 and the end of March 2024.

The temperature anomaly over the Great Lakes from December 2023 thru February 2024 is shown in Figure 3. The exceptionally warmer than normal temperatures are shown in this figure by the red color indicating a warmer than normal temperature anomaly over Lakes Erie and Ontario and by a burgundy color over the remainder of the Great Lakes indicating a warmer than normal temperature anomaly of more than 4°C.

The amount of ice on the Great Lakes after the very warm month of December 2023 is shown in Figure 4. On January 1, 2024, the ice that is usually present in shallow and protected areas such as the bays in northwestern Lake Superior, Saginaw Bay, Western Basin of Lake Erie, Lake St. Clair and southern Green Bay were all ice free and this is seen by the red color in Figure 4 in those areas.

The first cold temperature anomaly over the Great Lakes this season. It shows in purple temperatures 5-6°C colder than normal over southwestern Lake Superior, southern Lake Michigan and over Lake Erie. Figure 5 also shows in blue color that the rest of the Great Lakes were 2-4°C colder than normal during this cold period.

Departure from normal chart where blue areas with greater amounts of ice cover than is normal for the date of January 22^nd which is after the season’s first cold period. The areas in blue in figure 6 are along the southern shore of Lake Superior, along the southern and western shores of Lake Michigan, along the shore of Lake Huron, in Saginaw Bay, and along the shores of Lake Erie and southern Lake Ontario.

The departure from normal of lake ice coverage on the Great Lakes. The figure shows areas on the Great Lakes shown in red where there would usually be ice at the end of January and where this year there is no ice. The areas shown in red in Figure 7 are present in all the Great Lakes and there is no area in blue in any of the Great Lakes showing more ice than is the normal for the end of January. The areas in red over Lake Superior are along the southern shore and over Whitefish Bay. Over Lake Michigan, red areas showing less ice than normal are seen along the extreme southern shore and in Green Bay as well as the entire northeast corner of the lake. The shores of Lake Huron are colored red showing less ice than is usual as well as northeastern Georgian Bay and the Northern Channel. Almost all of Lake Erie is colored red showing no ice when usually in those areas at the end of January there is ice present, and the northeast corner of Lake Ontario is also shown in red in Figure 7 as not having ice cover when usually ice is present in that area of the lake.

The temperature anomaly over the Great Lakes on January 26^th. Figure 8 below shows in orange the above normal air temperature anomaly was 6-8°C above normal for the southern Great Lakes and in red 12-14°C above normal temperatures over the northern Great Lakes.

Figure 9 below shows the air temperature anomaly over the Great Lakes for the entire month of January. It shows that even with the season’s first ice-forming cold spell near the middle of the month of January, that for the entire month on average above normal air temperature of between 4-6°C occurred over the Great Lakes increasing to 6-8°C above normal for Lake Superior.

Figure 10 below shows that the average temperature experienced during the month of February was warmer than normal. The warm temperature anomaly over the Great Lakes for February is shown in Figure 10 below as 4-6°C above normal and over 7°C above normal in the Thunder Bay area.

The departure from normal of lake ice coverage on the Great Lakes on February 26^th. The figure shows areas on the Great Lakes shown in red where there would usually be ice at the end of February and where this year there is no ice. The areas shown in red in Figure 11 are in all the Great Lakes and there is no area in blue in any of the Great Lakes showing more ice than is the normal for the end of February. The areas covered in red cover all of Lake Erie; the northeast corner of Lake Ontario; all Georgian Bay, southern Lake Huron, Green Bay, northeastern Lake Michigan; and most of the shores of Lake Superior including Whitefish Bay.

Air temperatures were warmer than normal during the month of March. Temperatures over most of the Great Lakes were 3-5°C above normal temperatures for the month. Temperatures were a little closer to normal over the northwestern part of Lake Superior where temperatures averaged only 1-2°C warmer than normal for the month.

The cold air anomaly on March 21^st during its peak with air temperatures 6-8°C below normal for the period over most of the Great Lakes and becoming as much as 10-12°C below normal over northwestern Lake Superior.

A warm temperature anomaly during the month of March that occurred over the Great Lakes. Figure 14 shows that the area along the northwest shore of Lake Superior averaged 2°C warmer for the month of March than is normal while the rest of the Great Lakes were even warmer than is normal averaging 4-5°C warmer than normal for the month.

The mean temperature over the Great Lakes for the month of March. It shows the mean temperature was 3-4°C over Lakes Erie and Ontario and southern Lakes Huron and Michigan during March becoming near 0°C over Georgian Bay and the North Channel and dipping to 1-4°C below zero over Lake Superior.

The departure from normal of lake ice coverage on the Great Lakes on March 18^th. The Figure shows areas on the Great Lakes shown in red where there would usually be ice at the end of February and where this year there is no ice. These areas are seen in Figure 16 to be along the shores of Lake Superior, the entire area of Green Bay, the northeast corner of Lake Michigan, all of Georgian Bay and the North Channel, all of Saginaw Bay, and the southeastern corner of Lake Erie. There is no area in blue in any of the Great Lakes showing more ice than is the normal for mid-March.

With a green line the median coverage from 1990 to 2020 over the Great Lakes and with the blue vertical bars showing this seasons and last season’s weekly ice coverage amounts. Both seasons show much less ice coverage amounts than normal as the weekly blue vertical lines all lie well below the green curve showing the historical median ice concentration.

With a green line the climatological median ice coverage over the Great Lakes and this season’s weekly ice coverage amounts as blue bars. The only weekly ice coverage value to attain the historic median ice concentration occurred the week of January 22^nd during the maximum ice coverage over the Great Lakes. All other weeks’ ice coverage values are shown to be significantly below the historic mean value.

The yearly total accumulated ice coverage (TAC) in the Great Lakes since records started in 1973.

The yearly maximum ice coverage on the Great Lakes since records began in the 1972=1973 season.

The Great Lakes regional chart from January 22^nd, 2024, at the lake ice coverage maximum. Ice lined most of the shoreline and filled most of the bays in each lake. Lake St. Clair and the western basin of Lake Erie are also filled with ice. The maximum coverage occurred 4 weeks earlier than normal and was well under the climatological maximum.

Figure 22 above shows the ice coverage this year over Lake Superior as a black line with all past seasons represented by light blue lines and the historical average as a red line. The black line representing this year’s ice coverage in Figure 22 is significantly below the red line representing the median average year’s ice coverage giving a visual indication of how much less ice coverage was on the Great Lakes this year than is the normal. The black line representing this year’s ice coverage becomes flat at a value of zero about a month earlier at the end of the season and remained very close to zero for about a month at the start of the season while the red curve representing the average ice coverage year shows ice coverage is normally present at these times. This is indicating how much shorter this ice season was to the average length.

Figure 23 above shows with a green line the median ice coverage from 1990 to 2020 over Lake Superior and the blue vertical bars show this and last seasons’ weekly ice coverage amounts. Both seasons show much less ice coverage amounts than normal as the weekly blue vertical lines all lie well below the green curve showing the historical median ice concentration. This year’s ice coverage was about half that of last year’s as the blue monthly bars are half as tall as last year’s in Figure 23 above.

Figure 24 above shows with a green line the historical median ice coverage over the Lake Superior and this season’s weekly ice coverage amounts as blue bars. The only weekly ice coverage value to attain a value close to the historic median ice concentration occurred the week of January 22^nd during the maximum ice coverage over the Great Lakes. All other weeks’ ice coverage values are shown to be significantly below the historic mean value. The maximum ice coverage over Lake Superior is seen to take place on February 19^th as that is the week in Figure 24 with the highest blue vertical bar. This is about a month earlier than normal for the maximum ice coverage over Lake Superior as seen by the peak in the green line showing the historical ice cover on the lake occurring on March 19^th.

Figure 25 above shows the yearly total accumulated ice coverage (TAC) in Lake Superior since records started in 1973.

Figure 26 above shows the yearly maximum ice coverage on Lake Superior since records began in the 1972-1973 season.

Figure 27 above shows the ice coverage this year over Lake Michigan as a black line with all past seasons represented by light blue lines and the historical average as a red line. The black line is significantly below the red line giving a visual indication of how much less ice coverage was on Lake Michigan this year than is the normal. Only once in late January does the black line touch the red line. The black line is flat at a value of zero for about a month both at the start and at the end of the season while the red curve  shows ice coverage is normally present at these times, indicating this ice season was almost two months shorter than the average season.

Figure 28 above shows with a green line the median coverage from 1990 to 2020 over the Lake Michigan and with blue vertical bars shows this and last seasons’ weekly ice coverage amounts. Both seasons show much less ice coverage amounts than normal as the weekly blue vertical lines almost all lie well below the green curve showing the historical median ice concentration. Only one time this year did the weekly ice coverage on Lake Michigan attain the historical average value and that occurred during the season’s first cold spell on January 22^nd when the ice coverage on Lake Michigan surpassed the historical average value. This was the only time this year that the ice coverage on Lake Michigan approached the historical average ice amount as seen in Figure 28 by noting that no other blue bar showing the weekly ice coverage amounts approaches the green median ice concentration line.

Figure 29 below shows the weekly ice coverage on Lake Michigan. The green line represents the climatological median ice coverage over Lake Michigan, This season’s weekly ice coverage amounts are shown by vertical blue bars. The only weekly ice coverage value to attain a value close to the historic median ice concentration occurred the week of January 22^nd during the maximum ice coverage over the Great Lakes. All other week’s ice coverage values are shown to be significantly below the historic mean value. Also indicated by Figure 29 is how much shorter this year’s ice season has been than is normal. This is shown by noting that the vertical blue bars indicating the amount of ice cover on Lake Michigan each week are essentially at zero for 5 weeks after the normal start of the season as shown by the green line and again at zero 5 weeks before the normal end of the ice season.

Figure 30 above shows the yearly total ice accumulated coverage (TAC) in Lake Michigan since records started in 1973.

Figure 31 above shows the yearly maximum ice coverage on Lake Michigan since records began in the 1972-1973 season.

Figure 32 above shows the ice coverage this year over Lake Huron as a black line with all past seasons represented by light blue lines and the historical average as a red line. The black line representing this years’ ice coverage in Figure 32 is significantly below the red line representing the median average years’ ice coverage giving a visual indication of how much less ice coverage was on Lake Huron this year than is the normal. The black line representing this year’s ice coverage is flat at a value of zero for about a month both at the start and at the end of the season while the red curve representing the average ice coverage year shows ice coverage is normally present at these times, indicating this ice season was about 6 weeks shorter than the average season.

Figure 33 below shows with a green line the climatological median ice coverage over the Lake Huron and Georgian Bay and with blue vertical bars shows this and last seasons’ weekly ice coverage amounts. The low ice coverage this year as well as last is shown by the vertical blue bars indicating the weekly amount of ice coverage on Lake Huron being consistently significantly below the green line representing the historical ice coverage on Lake Huron.

Figure 34 above shows the weekly ice coverage on Lake Huron. The green line represents the climatological median ice coverage over Lake Huron and this season’s weekly ice coverage amounts are shown by vertical blue bars. The only weekly ice coverage value to attain a value close to the historic median ice concentration occurred the week of January 22^nd during the maximum ice coverage over the Great Lakes. All other weeks’ ice coverage values are shown to be significantly below the historic mean value. Also indicated by Figure 34 is how much shorter this year’s ice season has been than is normal. This is shown by noting that the vertical blue bars indicating the amount of ice cover on Lake Huron each week are essentially at zero for 4 weeks after the normal start of the season as shown by the green line and again at zero 5 weeks before the normal end of the ice season.

Figure 35 above shows the yearly total ice accumulated coverage (TAC) in Lake Huron since records started in 1973.

Figure 36 above shows the yearly maximum ice coverage on Lake Huron since records began in the 1972-1973 season.

Figure 37 above shows the ice coverage this year over Lake Erie as a black line with all past seasons represented by light blue lines and the historical average as a red line. The black line representing this years’ ice coverage in Figure 37 is significantly below the red line representing the median average years’ ice coverage giving a visual indication of how much less ice coverage was on Lake Erie this year than is the normal. The black line representing this year’s ice coverage is flat at a value of zero for about a month both at the start and at the end of the season while the red curve representing the average ice coverage year shows ice coverage is normally present at these times, indicating this ice season was about 10 weeks shorter than the average season.

Figure 38 above shows with a green line the historical median ice coverage over the Lake Erie for this year and last year and with blue vertical bars shows this seasons and last season’s weekly ice coverage amounts. Both seasons show much less ice coverage amounts than normal as the weekly blue vertical lines all lie well below the green curve showing the historical median ice concentration.

Figure 39 above shows with a green line the historical median ice coverage over the Lake Erie and this season’s weekly ice coverage amounts as blue bars. The only weekly ice coverage value to attain a value close to the historic median ice concentration occurred the week of January 22^nd during the maximum ice coverage over the Great Lakes. All other week’s ice coverage values are shown to be significantly below the historic mean value. Figure 39 above also displays how the ice season both started 3 weeks later than normal as well as ended 6 weeks earlier than normal.

Figure 40 above shows the yearly total accumulated ice coverage (TAC) in Lake Erie since records started in 1973.

Figure 41 above shows the yearly maximum ice coverage on Lake Erie since records began in the 1972-1973 season.

Figure 42 above shows the ice coverage this year over Lake Ontario as a black line with all past seasons represented by light blue lines and the historical average as a red line. The black line representing this years’ ice coverage in Figure 42 is significantly below the red line representing the median average years’ ice coverage giving a visual indication of how much less ice coverage was on Lake Ontario this year than is the normal. The black line representing this year’s ice coverage is flat at a value of zero for about a month both at the start and at the end of the season while the red curve representing the average ice coverage year shows ice coverage is normally present at these times, indicating this ice season was about 6 weeks shorter than the average season.

Figure 43 above shows with a green line the historical median ice coverage over the Lake Ontario for this year and last year and with blue vertical bars shows this seasons and last season’s weekly ice coverage amounts. Both seasons show much less ice coverage amounts than normal as the weekly blue vertical lines all lie well below the green curve showing the historical median ice concentration. Figure 43 also shows that though both this and last season had low amounts of ice on Lake Ontario that this season also ended abruptly 5 weeks early as shown by the weeks ice cover amounts going to zero on March 12^th as opposed to the usual date of April 5^th when the green line representing the historical ice cover amount trends to zero.

Figure 44 above shows with a green line the historical median ice coverage over the Lake Ontario and this season’s weekly ice coverage amounts as blue bars. The only weekly ice coverage value to match the historic median ice concentration occurred the week of January 22^nd during the maximum ice coverage over the Great Lakes. All other week’s ice coverage values are shown to be significantly below the historic mean value. Figure 44 above also displays how the ice season both started 2 weeks later than normal as well as ended 5 weeks earlier than normal.

Figure 45 above shows the yearly total accumulated ice coverage (TAC) in Lake Ontario since records started in 1973.

Figure 46 above shows the yearly maximum ice coverage on Lake Ontario since records began in the 1972-1973 season.