Douglas County Climate Profile

Douglas County is located in the northwestern part of Wisconsin, with Lake Superior bordering the county to the north. The land cover of Douglas County is primarily forests, along with wetlands and open grass/pasture. The City of Superior, Douglas County’s largest urban area, is along the shores of Lake Superior in the northwest part of the county.

Douglas County has a humid continental climate, characterized by precipitation year-round and summers that are warm to hot. Lake Superior has a localized effect on Douglas County’s climate, especially along the shores. The lake can moderate temperatures of northern Douglas County, such as keeping things cooler during the day in summer and warmer during the night in winter. Lake Superior also plays a key role in other Douglas County weather phenomena, such as lake-effect snow events and strong winds in fall.

Records are computed using all available station data, some of which goes back to 1895. Records are from the period 1895-2024 (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 Douglas County on the annual and seasonal time scales, which is the case for most of Wisconsin. Since 1950, annual average temperatures in Douglas County have increased at a rate of 0.5°F/decade, which translates to an increase of 1°F every 20 years. This increase in temperature has been most pronounced in the winter months and less pronounced in the other seasons. When annual average temperatures are split into daily high and low temperatures, low temperatures have been warming at a faster rate compared to high temperatures across most seasons.

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 (1895-2024) temperatures. However, Douglas County is experiencing more years that are above average than it did in the past. For example, since 2000, Douglas County has experienced only five years with below-average temperatures. Similarly, if we rank the top ten warmest years in Douglas County since 1895 (black circles on the above chart), six have occurred since 2000. The years of 1998 and 1999 also rank in the top ten. The top ten coldest years (black squares) are a bit more clustered towards the earlier years in this time period, with all of the top ten years occurring before 2000.

On the annual timescale, precipitation has shown minimal change in Douglas County since 1950. Precipitation has decreased at a rate of 0.10″ per decade, which means a decrease of one inch every 100 years. At the seasonal level, summer is the season of largest decrease in precipitation in terms of inches per decade (-0.26″ per decade) and percentage (-13%) since the early 1950s. Conversely, fall is the season of largest increase in precipitation in terms of inches per decade (0.30” per decade) and percentage (14%).

Looking at the full record from 1895 to 2024, annual precipitation has increased overall (one inch approximately every 33 years). However, as was noted in previous paragraph, there is a slight decrease if the trend starts in 1950. Taken together, the two graphs show that trends across shorter time periods can be more affected by the ups and downs in weather, pointing to the usefulness of long-term data sets when looking at climate trends. Even within the long-term trend that shows increasing precipitation, year-to-year precipitation varies. Since 2000, for example, the county has had three of its wettest years on record (2013, 2014, 2016), but it has also seen 13 years with below-average precipitation. This mix of wet and dry years is normal within a long-term trend.

Douglas 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 Douglas 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 Douglas County. Based on this analysis, hot days have occurred most frequently between July 21 to 31. Warm nights have been most common from August 1 to 10. Over the past 20 years (2005-2024), Douglas County experienced, on average, 12 hot days per year and three warm nights per year.

Have Douglas County summers been getting hotter? It depends on what variable you are looking at. Since 1950, most of the summer warming has been occurring in the nighttime hours. Summertime low temperatures have warmed by about 3°F since 1950.  By comparison, summer high temperatures in Douglas County have not warmed as much (1-2°F). You can read more about trends in summertime temperatures in Wisconsin in this blog post.

Douglas 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 Douglas County. Based on this analysis, very cold days and nights have occurred most frequently between January 21 to 31. Over the past 20 years (2005-2024), Douglas County experienced, on average, 19 very cold days per year and 52 very cold nights per year.

Across all four seasons, winter has warmed the most in Douglas County since 1950, a trend that holds true across most of Wisconsin. Since 1950, average winter temperatures in Douglas County have warmed by about 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 Douglas County has also 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 Douglas 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 (75 percent) have occurred from June through September. August is the month that has historically had the most heavy precipitation days in Douglas County. In general, summer is the wettest season in Douglas County, with winter being the driest season. Over the past 20 years (2005-2024), Douglas County experienced, on average, 12 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 Douglas 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 substantially as winters warm (20-30 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 is projected to increase with a warming climate to 20-25 days per year.

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 Douglas 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 Douglas 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.