September 2025 Climate Summary

La Crosse tied its daily high-temperature record of 87 degrees on September 29 (previously set in 1898), and Rhinelander broke its record with 82 degrees (previously 81 degrees in 1948). The hottest temperature of the month was a sizzling 92 degrees in Wausaukee (Marinette County) on September 18.

Overnight temperatures were remarkably warm for September. The preliminary statewide average minimum temperature for the month was 51.4 degrees (three degrees warmer than normal), estimated to be the sixth warmest on record since 1895.

Impressive streaks of above-normal low temperatures were recorded at all six first-order stations, including 19 consecutive days in Wausau and a nighttime temperature as much as 16 degrees warmer than normal recorded on September 18 (Figure 2).

Despite the frosty start, the warm finish carried the preliminary statewide average temperature to 62.3 degrees, which is 2.8 degrees above the 1991 to 2020 normal and estimated to be the 13th warmest September on record since 1895 (Figure 3).

A Few Drops in the Bucket

Wisconsin’s dry conditions from August bled into September. The Dane County Regional Airport in Madison reported precipitation on only five days during the month, the fewest rainy days in September since 2004! 

The rain that did fall didn’t amount to much in many places: the preliminary statewide average for the month was only 2.54 inches, 1.05 inches drier than average (Figure 4).

After missing out on much of the rain last month, central and northern Wisconsin received the most precipitation during September. Widespread monthly totals of two to four inches were seen in those regions.

Much of northern Wisconsin’s moisture came on September 9 and 10, with a complex of showers resulting in widespread reports of one to two inches.

Back-to-back systems on September 19 and 20 poured one to two inches of rain across the central and southern parts of the state, while northern Wisconsin was left with less than a half inch.

Morning and afternoon rounds of storms on September 22 dumped enough rain on La Crosse to tie the city’s daily rainfall record of 1.7 inches that had been previously reached in 1959. Totals across the rest of southern Wisconsin ranged from a half inch to two inches of rain for most, aside from Waukesha County, where many cities reported over two inches.

The end of September marks the end of the 2024-25 water year. The term has been used for nearly a century by hydrologists monitoring surface water supply, such as streamflow and runoff. Runoff data for water year 2025 will not be available for several months.

Severe Weather Season Hangs On

As temperatures cool and the atmosphere stabilizes during the autumnal months, thunderstorms and severe weather become less frequent in Wisconsin. Based on the issuance of warnings by the National Weather Service offices, severe weather activity typically halves in September compared to August (Figure 5). September 2025 was no different in Wisconsin.

Aside from a few storms dropping pea-sized hail through southern Wisconsin on September 13 and 20, the severe weather department was quiet across the state until September 22.

A morning round of thunderstorms rolled through the southern part of the state on September 22, taking down trees and power lines in Vernon County. Two lightning strikes in the county caused power outages in the village of Stoddard, but no injuries were reported. 

Unfortunately, in Fond du Lac County, a Wisconsin Department of Natural Resources forestry worker was caught out in the storm and was struck and killed by lightning. This marked the first lightning strike death in Wisconsin since August 2021, according to the National Lightning Safety Council.

A second round of storms developed during that same afternoon, hitting southern Wisconsin once again. Strong winds took down trees in parts of Jefferson and Waukesha counties, and a storm chaser estimated lime-sized hail (two inches) hit their car while driving through the storms from Grant to Iowa County.

A short-lived tornado was confirmed in Mount Sterling in Crawford County after minor damage to corn and farm buildings was observed by emergency managers (Table 4). This marks Wisconsin’s 39th tornado this year, tying the record for sixth most in the state in a calendar year.

Table 4. A summary of the one tornado that occurred in Wisconsin during September 2025. Information is from the National Weather Service.

September 2025 Tornadoes in Wisconsin
Location	Date	Enhanced Fujita (EF) Rating	Estimated Maximum Winds	Damage Reported
Mount Sterling (Crawford Co.)	September 22	EF0	75 mph	Minor damage to corn, outbuilding, and silo.

Dry Conditions Spread

Prolonged stretches of dry and hot weather through the month allowed abnormally dry conditions (D0) to spread across the state (Figure 6). Northern Wisconsin, especially, saw an increase in abnormal dryness, as did some parts of the southern region. 

A similar pattern was seen last September: Wisconsin was plagued with stretches of dry weather following a wet summer. By the end of September 2024, conditions were more severe, with many areas of moderate drought (D1) in the state (Figure 7). By the end of October 2024, the entire state was experiencing drought for the first time since at least 2000, with some areas of severe drought (D2). Hopefully, we won’t see a full repeat of that pattern this fall!

Harvest Begins

The early-month chill had gardeners covering tender plants and raised the possibility of frost damage in some areas. For corn, the cooler temperatures may have extended grain filling and produced heavier kernels in areas without frost. However, the below-normal temperatures, combined with a few drops of rain, likely slowed natural dry down. 

By the final weeks of September, the summerlike warmth was ideal for apple harvest and ripening pumpkins. Most pumpkins matured where excess rain or cold damage did not occur, though early frost-stricken fields may have seen halted growth.

The warmth also sped up the maturity of corn and soybeans. Corn silage harvest was already two-thirds complete statewide by month’s end, and farmers were planting cover crops into harvested fields, though dry soils made establishment difficult.

As farmers began to move grain to market, transportation challenges reemerged for the fourth year in a row. Extremely dry conditions along the Ohio River Basin and in the lower Midwest have led to low water levels on the Lower Mississippi River, once again restricting tow sizes and increasing barge rates. Southbound grain shipments plunged from 2.4 million short tons (one short ton equals 2,000 pounds) in August to 502 thousand short tons in September, a 79 percent drop.

Lost in the Fog

As temperatures drop during the fall, fog becomes more common as moisture condenses in the cool air. However, some northern areas of the state battled dense fog more frequently than normal in September, causing visibility to drop to a quarter-mile or less on many mornings! 

The airport in Green Bay reported visibility under a quarter mile for 73 hours of the month — the second most on record for the city (Figure 8)!

Even farther north, Ashland (Ashland County) experienced its foggiest September on record with 112 hours of dense fog! Eight dense fog advisories were issued for Ashland and Bayfield counties through the month, the most of any month for those counties since 2009.

Thanks to mild overnight temperatures, many areas farther south avoided the persistent fogginess.

Dancing Lights in the Night

Wisconsin was treated to at least three nights of northern lights this September — on September 1, 14, and 29. 

While a visit from the aurora requires many factors to align, these sightings weren’t purely by chance. The aurora is most likely to glow here between September and March, when long nights and crisp, clear skies provide the best backdrop. 

Fall and spring equinoxes, around September 21 and March 21, also tend to align with a boost in geomagnetic activity — making September a prime month for skywatchers to catch the colorful display (Image 2).

Climate Corner

Arguably, the most anticipated characteristic of fall is the changing colors of the trees (unless you’re a football fan). Weather plays a huge role in the timing, longevity, and vibrancy of the state’s fall scenery — but did you know that certain colors dominate different regions? Whether you’re partial to deep burgundys or fiery oranges, learn where to find them in Wisconsin in this month’s Climate Ed-ucation blog!

Climate State by Division

These tables will be published once NOAA’s National Centers for Environmental Information (NCEI) updates their official database.