Brown County Climate Profile

Brown County is located in the east-central part of Wisconsin, along the shores of the Green Bay. The county’s land cover is a blend of agriculture, grasslands/pasture, and wetlands. There is also a large amount of urban development in the county with the City of Green Bay and surrounding communities. Some of the Oneida Nation call the county home, after the reservation was established in Brown and Outagamie Counties in 1838. 

Brown County has a humid continental climate, characterized by precipitation year-round and summers that are warm to hot. Green Bay has a localized effect on Brown County’s climate. This bay of Lake Michigan can moderate temperatures of Brown County, such as keeping things cooler during the day in summer and warmer during the night in winter. Lake Michigan also plays a key role in other Brown County weather phenomena, such as lake-effect snow events, dense fog, and strong winds in fall.

Records are computed using all available station data, some of which goes back to 1895 (Source: ACIS).

Averages for freeze dates are computed for the most recent 30 years (1995-2024; Source: ACIS).

Temperatures have been increasing since 1950 in Brown County on the annual and seasonal time scales, which is the case for most of Wisconsin. Since 1950, annual average temperatures in Brown County have increased at a rate of 0.6°F/decade, which translates to an increase of 1°F every 17 years. This increase in temperature has been most pronounced in the winter months and less pronounced in the summer months. When average temperatures are split into daily high and low temperatures, low temperatures have been warming at a faster rate compared to high temperatures. In particular, winter minimum temperatures have been increasing by 1°F every 10 years since 1950.

With temperatures warming, this does not mean that every year will be warmer than the last, or that more recent years will all have above-average (1895-2025) temperatures. However, Brown County is experiencing more years that are above average than it did in the past. For example, since 2000, Brown County has experienced just four years with below-average temperatures. Similarly, if we rank the top ten warmest years in Brown County since 1895 (black circles on the above chart), seven have occurred since 2000, with 1998 also ranking in the top ten. The top ten coldest years (black squares) are more concentrated in the earlier years of this time period, with all of the top ten years occurring before 2000.

On the annual timescale, precipitation has been increasing at a rate of 0.90″ per decade since 1950, which translates to an increase of one inch approximately every 11 years. At the seasonal level, precipitation has been increasing across all seasons. Summer is the season of largest increase in precipitation in terms of inches per decade (0.40”/decade) and in terms of the largest percentage increase from average annual precipitation in the early 1950’s (30%). It is less common in Wisconsin that summer is the season with largest percentage increase, as most counties have seen the largest percentage increase in winter.

Annual precipitation shows a lot of year-to-year variability, which is normal within a long-term trend. However, there are two notable trends that come from this dataset. First, precipitation is increasing at a rate of 0.33 inches per decade from 1895 to 2025. That’s an increase of one inch approximately every 30 years. Second, if we look at the past 20 years (2006-2025), Brown County has had five of its top ten wettest years since 1895 (black circles) and just five years have been drier than the long-term (1895-2025) average. By contrast, of the top ten driest years (black squares), all occurred prior to 2000. These trends are quite similar to what has been observed in Brown County with temperatures since 1895.

Brown County is no stranger to sweltering summer heat, where daytime temperatures can top 90°F or even 100°F. But when are these hot days most likely to occur in Brown County? The State Climatology Office analyzed the likelihood of a “hot day” (daily high temperature ≥ 90°F) or “warm night” (daily low temperature ≥ 70°F) occurring between two calendar dates using historical measured temperature data from NOAA stations in Brown County. Based on this analysis, hot days have occurred most frequently between July 21-31, and warm nights most frequently between July 11-20. Over the past 20 years (2006-2025), Brown County experienced, on average, 11 hot days per year and six warm nights per year.

Have Brown County summers been getting hotter? Since 1950, summertime average temperatures have warmed by about 3°F, but have not warmed as much compared to other seasons in Brown County. Summertime low temperatures have warmed by about 4°F since 1950. By comparison, summer high temperatures in Brown County have not warmed as much (1.5°F). You can read more about trends in summertime temperatures in Wisconsin in this blog post.

Brown County can get quite chilly once winter rolls around! Some of our coldest days of the year in Wisconsin are when the overnight low temperatures dip below 0°F. The State Climatology Office performed an analysis on the likelihood of a “very cold day” (daily high temperature ≤ 10°F) or “very cold night” (daily low temperature ≤ 0°F) occurring between two calendar dates using historical measured temperature data from NOAA stations in Brown County. Based on this analysis, very cold days and nights have occurred most frequently between January 21 to 31. Over the past 20 years (2006-2025), Brown County experienced, on average, 10 very cold days per year and 25 very cold nights per year.

Across all four seasons, winter has warmed the most in Brown County since 1950, a trend that holds true across most of Wisconsin. Since 1950, average winter temperatures in Brown County have warmed by approximately 6°F. Over this same time period, low temperatures in winter have warmed a bit more than the average temperatures (7-8°F). The coldest temperature of the year in Brown County has shown a warming trend since 1950.

Heavy precipitation days, which for this publication refers to a one-day liquid precipitation total of two inches or more, can impact Brown County at all times of the year. Extreme precipitation in the winter is measured by the amount of liquid that would be present if you melted down all of the snow that fell that day. The vast majority of these heavy precipitation days (76 percent) have occurred from June through September. August is the month that has historically had the most heavy precipitation days in Brown County. In general, summer is the wettest season in Brown County, with winter being the driest season. Over the past 20 years (2006-2025), Brown County experienced, on average, seven heavy precipitation days per decade.

Future climate projections from the Wisconsin Initiative on Climate Change Impacts (WICCI) indicate that by mid-century (2041-2060) under a moderate greenhouse gas emissions scenario, average annual temperatures in Brown County will continue to increase by approximately 4°F compared to recent averages. Winter is projected to continue to be the season of the largest temperature increase (about 5°F). The number of nights where temperatures drop below 0°F is expected to decrease as winters warm (about 5-10 per year), and the number of nights in summer with temperatures staying above 70°F is expected to increase. The frequency of days that top 90°F are projected to increase with a warming climate (20 to 25 days per year). Days that top 100°F have been relatively rare in Brown County up to 2025, but WICCI projections indicate that temperatures will hit 100°F a few days per year by mid-century.

Annual precipitation is expected to increase by around five percent by mid-century, according to WICCI projections. Winter and spring are projected to be the seasons of greatest precipitation increase in Brown County (about 10%), with summers projected to be 5% drier by mid-century. Despite projections for drier summers, the frequency of heavy precipitation days (two inches or more) is projected to increase by mid-century. 

To explore more climate projections from WICCI and learn more about future climate modeling, please visit this website.

The data in this publication are a snapshot of the historical climate data for Brown County. If you have questions about this publication or would like more data on a topic, please contact the Wisconsin State Climatology Office. 

For more information about how climate affects your farm, community, health, and livelihood, please check out these resources from the Division of Extension and the Wisconsin Initiative on Climate Change Impacts.