Ashland County Climate Profile

Ashland County is located in the northwestern part of Wisconsin, with Lake Superior bordering the county to the north. The land cover of Ashland County is primarily forests, along with wetlands/open water and agricultural lands. The City of Ashland, Ashland County’s largest city, is along the shores of Lake Superior in the northwest part of the county. Some of the Ojibwe Bad River Band call the county home, after the reservation was established in Ashland County and neighboring Iron County in 1854. Ashland County is also home to the Apostle Islands National Lakeshore.

Ashland 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 Ashland County’s climate, especially along the shores. The lake can moderate temperatures of northern Ashland 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 Ashland 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).

*NOTE: The record one-day rainfall reported at Mellen is currently the state record.

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

Temperatures have been increasing since 1950 in Ashland County on the annual and seasonal time scales, which is the case for most of Wisconsin. Since 1950, annual average temperatures in Ashland County have increased at a rate of 0.4°F/decade, which translates to an increase of 1°F every 25 years. This increase in temperature has been most pronounced in the winter months and less pronounced in the other seasons. When winter average temperatures are split into daily high and low temperatures, low temperatures have been warming at a faster rate (1°F every 11 years) compared to high temperatures.

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, Ashland County is experiencing more years that are above average than it did in the past. For example, since 2000, Ashland County has experienced only six years with below-average temperatures. Similarly, if we rank the top ten warmest years in Ashland County since 1895 (black circles on the above chart), seven have occurred since 2000, with 1998 coming in as the warmest year on record. 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 Ashland County since 1950. Precipitation has decreased at a rate of 0.03″ per decade, which means a decrease of less then one inch every 100 years. At the seasonal level, summer is the season of largest decrease in precipitation in terms of inches per decade (-0.31″ per decade) and percentage (-15%) since the early 1950s. Conversely, winter is the season of largest increase in precipitation in terms of percentage (26%).

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. 

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

Have Ashland County summers been getting hotter? Since 1950, summertime average temperatures have warmed by 1-2°F, but have not warmed as much compared to other seasons in Ashland County. Summertime high temperatures and low temperatures have been warming at similar rates (1-2°F). You can read more about trends in summertime temperatures in Wisconsin in this blog post.

Ashland 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 Ashland 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), Ashland County experienced, on average, 19 very cold days per year and 48 very cold nights per year.

Across all four seasons, winter has warmed the most in Ashland County since 1950, a trend that holds true across most of Wisconsin. Since 1950, average winter temperatures in Ashland 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 (6.5-7°F). The coldest temperature of the year in Ashland 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 Ashland 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 (74 percent) have occurred from June through September. July is the month that has historically had the most heavy precipitation days in Ashland County. In general, summer is the wettest season in Ashland County, with winter being the driest season. Over the past 20 years (2005-2024), Ashland’s Kennedy Memorial Airport experienced, on average, 8 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 Ashland 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 (15-25 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 15-25 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 Ashland 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 Ashland 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.