Updated October 2026
Effigy Mounds National Monument Weather by Month
Effigy Mounds National Monument is warmest in July, when the nearest NOAA climate station averages a high of 83°F and a low of 63°F, and coldest in January, with an average high of 27°F and an average low of 10°F. June is the wettest month, with about 5.8 inches of precipitation. Snowfall is heaviest in January, at about 9 inches.
These figures are NOAA's 1991–2020 climate normals, the 30-year average for each calendar month, from the nearest long-record weather station, 3.7 miles from the park's reference point. A single station cannot describe a whole park: temperatures elsewhere in Effigy Mounds National Monument can differ from these, particularly with elevation.
Warmest month
Jul
83°F avg high
Coldest month
Jan
10°F avg low
Wettest month
Jun
5.8 in avg
Snowiest month
Jan
9.0 in avg
Longest days
Jun
15.2 h of daylight
Average weather at Effigy Mounds by month
| Month | Avg high | Avg low | Precipitation | Snowfall | Daylight |
|---|---|---|---|---|---|
| January | 27°F | 10°F | 1.2 in | 9.0 in | 9.2 h |
| February | 32°F | 13°F | 1.3 in | 8.6 in | 10.3 h |
| March | 45°F | 25°F | 2.1 in | 4.3 in | 11.6 h |
| April | 59°F | 37°F | 4.0 in | 1.4 in | 13.2 h |
| May | 70°F | 48°F | 4.7 in | 0.0 in | 14.5 h |
| June | 80°F | 59°F | 5.8 in | 0.0 in | 15.2 h |
| July | 83°F | 63°F | 4.1 in | 0.0 in | 14.9 h |
| August | 81°F | 61°F | 4.2 in | 0.0 in | 13.8 h |
| September | 74°F | 52°F | 4.0 in | 0.0 in | 12.3 h |
| October | 62°F | 40°F | 2.7 in | 0.2 in | 10.8 h |
| November | 46°F | 28°F | 2.1 in | 1.5 in | 9.5 h |
| December | 33°F | 17°F | 1.6 in | 8.8 in | 8.8 h |
| Year total | 37.8 in | 33.8 in |
NOAA 1991–2020 climate normals from station USC00476827, 3.7 miles from the park's reference point. Daylight is the monthly average, computed from the park's latitude. Each month links to how crowded Effigy Mounds is at that time of year.
Effigy Mounds weather by season
Winter: December to February
Average highs bottom out at 27°F in January, between 33°F in December and 32°F in February, with average lows between 10°F and 17°F. The average low is at or below freezing in all three months. Together the three months average 4.1 inches of precipitation, about 11% of the yearly total and less than in any other season. Snowfall averages about 26 inches for the season. Daylight is at its shortest, about 8.8 hours in December.
Spring: March to May
Average highs climb from 45°F in March to 70°F in May, with average lows between 25°F and 48°F. The average low is at or below freezing in March. Together the three months average 10.8 inches of precipitation, about 29% of the yearly total. Snowfall averages about 5.7 inches for the season, most of it in March. Daylight lengthens from about 11.6 hours in March to 14.5 in May.
Summer: June to August
Average highs peak at 83°F in July, between 80°F in June and 81°F in August, with average lows between 59°F and 63°F. Together the three months average 14.1 inches of precipitation, about 37% of the yearly total and more than in any other season. Daylight is at its longest, about 15.2 hours in June.
Fall: September to November
Average highs fall from 74°F in September to 46°F in November, with average lows between 28°F and 52°F. The average low is at or below freezing in November. Together the three months average 8.8 inches of precipitation, about 23% of the yearly total. Snowfall averages about 1.7 inches for the season, most of it in November. Daylight shortens from about 12.3 hours in September to 9.5 in November.
What the National Park Service says about the weather
All four seasons are represented in this area with summer temperature in the upper 80’s with higher heat indexes due to humidity and winter daytime highs in the 20's. Temperatures are in °Fahrenheit.
Weather description courtesy of the National Park Service — official park site.
Today's forecast for Effigy Mounds
Averages describe a typical month, not this week. For current conditions and the seven-day outlook, the National Weather Service issues a forecast for the park's reference point at 43.08°N, 91.20°W. It covers that one spot, so other elevations in the park can differ from it, as they do from the averages above.
National Weather Service forecast for Effigy Mounds National Monument →
Weather and crowds together
July is both the warmest month and the busiest, with about 2.0× the visitors of the park's average month. December is the quietest. To see those crowds set against the weather for all twelve months, read the best time to visit Effigy Mounds National Monument. For hotels, cabins and rentals close to the park, see where to stay near Effigy Mounds.
Where to stay near Effigy Mounds
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Frequently Asked Questions
July is the warmest month at Effigy Mounds National Monument, with an average high of 83°F and an average low of 63°F. That is the 1991–2020 average at the nearest long-record NOAA station, 3.7 miles from the park's reference point. Temperatures inside the park can differ, particularly with elevation.
January is the coldest month at Effigy Mounds National Monument, with an average low of 10°F and an average high of 27°F, based on NOAA 1991–2020 climate normals.
June is the wettest month, with about 5.8 inches of precipitation. January is the driest, at about 1.2 inches. The station records about 37.8 inches of precipitation in an average year.
Yes. The nearest long-record NOAA station, 3.7 miles from the park's reference point, averages about 34 inches of snow a year. January is the snowiest month, at about 9 inches. The station averages at least a tenth of an inch of snow in 7 of the 12 months.
Weather at nearby parks
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Sources: NOAA NCEI U.S. Climate Normals 1991–2020 (station USC00476827), daylight computed from latitude, weather description from the National Park Service, crowd levels from National Park Service Visitor Use Statistics (1979–2025). Updated 2026-10-11. Lodging results are provided by Stay22; WhenToVisitParks may earn a commission from bookings, at no extra cost to you.