August and summer 2024 climate summary

Editor’s Note: The following climate summary was provided by the Wisconsin State Climatology Office.

Editor’s Note: The following climate summary was provided by the Wisconsin State Climatology Office.

The last month of meteorological summer ended with an intense heatwave; however, temperatures averaged near normal for August and the entire summer.

Wisconsin experienced a “temperature parfait” during August, consisting of three distinct thermal periods. The month started with several days of hot weather, beginning with scores of stations reaching at least 90 degrees Aug. 1. A 94-degree afternoon greeted visitors at the opening of the Wisconsin State Fair in West Allis.

The statewide average temperature from August 1-5 was 5 degrees warmer than normal. A long stretch of comfortable conditions immediately ensued, with temperatures running below normal by 2 degrees until Aug. 23. However, the taste of early fall was displaced by an intense heat wave during the final week of August that led to a statewide average temperature of 5 degrees warmer than normal, matching the warm conditions that started the month.

For August as a whole, these temperature swings mostly canceled each other and resulted in a Wisconsin monthly average of 67.7 degrees, only 0.5 degrees warmer than normal.

For the second year in a row, a late-August heat wave generated the hottest weather of the year and led to the National Weather Service issuing an excessive heat warning. A slew of daily temperature records was set throughout the state during the heatwave from Aug. 26-29.

The highest temperature of the year (98 degrees) occurred at three locations: Beloit and Brodhead in the far south and Mondovi in the west. The heat was accompanied by stifling humidity, with widespread dewpoint temperatures in the middle to upper 70s and a couple of stations (Boscobel and Lone Rock) touching 80 degrees.

This combination of extreme heat and moisture produced dangerously high heat indices of at least 110 degrees in a few places. This heat wave was short-lived and considerably less intense than the August 2023 event, when the air temperature alone exceeded the century mark in many places and included a statewide maximum for the year of 105 degrees.

Wisconsin saw a statewide average of 4.28 inches of precipitation this August, which was 0.38 inches above the 1991 to 2020 normal of 3.90 inches. Despite August’s near-normal statewide amounts, rain fell infrequently, with measurable rainfall (at least 0.01 inches) occurring on fewer than half the days of August.

Southwestern Wisconsin was particularly parched as it saw just 6-9 days of rainfall by the end of August, resulting in precipitation amounts of only 50%-75% of normal for many counties. In contrast, central and northwestern Wisconsin compensated for the days of minimal precipitation with widespread high rainfall intensity events of 4-8 inches, resulting in accumulation well over 100% of normal. A few counties even neared 200% of normal.

A few rounds of thunderstorms the first week of August brought torrential downpours and reports of funnel clouds. However, the funnel clouds were short-lived and dissipated before reaching the ground.

Another round of severe storms struck Wisconsin in late August, coinciding with the extreme heat. By the end of the month, the hot and humid weather broke following a cold front, but along with the cold front came three tornadoes: two EF0s and one EF1. The EF1 tornado traveled 6.6 miles near Beldenville (Pierce County). One of the EF0 tornadoes crossed the St. Croix River and entered Pierce County. The other EF0 traveled 1 mile along Interstate 94 near Wilson (St. Croix County).

These three tornadoes bring this year’s count to 45, making it the third-highest total since records began in 1950. Although this year has appeared active in terms of the number of tornadoes, the 21 confirmed tornadoes for summer 2024 tied 1967 for 15th place, well behind the 58 tornadoes that hit the state in the summer of 2005. Of the 21 tornadoes this summer, half were weak EF0s.

Much like August itself, this year’s meteorological summer featured temperatures very close to normal throughout Wisconsin. The statewide summer average was 67.3 degrees, 0.1 degree above the 1991–2020 average, in sharp contrast to the fourth hottest summer on record experienced by the nation as a whole. Only in a few scattered places did daily average temperatures stray more than a degree from normal.

Hot weather in 2024 has been brief and — except for the late-August heat wave — not especially intense for Wisconsin.

In a typical year there are 10 days of at least 90 degrees at Wisconsin’s first-order weather stations (Eau Claire, Green Bay, La Crosse, Madison, Milwaukee and Wausau). By the end of summer this year, only six such hot days have occurred.

It also appears that Wisconsin will not record a 100-degree temperature in 2024. The absence of triple-digit heat is something that has become common in recent years, even though Wisconsin’s annual maximum temperature used to regularly surpass 100 degrees, based on data back to the 1880s.

Abnormal dryness reappeared in northern and southwestern Wisconsin by the end of July and end of August, respectively, as a result of below-normal precipitation. Despite the highly varying precipitation pattern, meteorological summer ended with a statewide average of 15.73 inches, a noteworthy 3.09 inches above normal and the sixth wettest summer on record.

The abundance of rainfall the first half of the summer made for difficult working and growing conditions. In August, nearly six days per week were suitable for fieldwork according to the National Agricultural Statistics Service. Despite the early summer challenges, Wisconsin’s corn and soybeans continued to progress, with a majority of crops remaining in good to excellent condition and hovering right around the five-year average pace throughout the summer.

While odds are again leaning toward a warm upcoming season (September through November) throughout most of the country, there is no indication whether Wisconsin or the Upper Midwest will experience an unusually wet or dry autumn. The National Weather Service’s outlook issued last month calls for a 40%-50% chance that Wisconsin’s fall season will be warmer than normal, with a somewhat stronger likelihood in the eastern portion. Since the late 1990s, nearly three out of four autumns in the state have been warmer than the long-term average (1895-present).