Iowa City climate — normals and trends
Iowa City (United States) has a hot-summer humid continental climate (Dfa) under the Köppen-Geiger classification. Its mean annual temperature is 9.5 °C and it receives 940 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is July (23.4 °C on average) and the coldest is January (-6.8 °C). Rainfall peaks in June.
Iowa City averages 127 frost days, 27 hot days (≥ 30 °C) and 108 rainy days per year.
Iowa City has warmed by +1.9 °C between 1940 and 2025, or +0.22 °C per decade. This trend is statistically significant.
The number of frost days there went from about 136 to 118 per year over the period.
The hottest day of the period reached 39.6 °C (on 16 August 1988) and the coldest -34.9 °C (on 16 January 2009).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
Iowa CityIowa
- coords
- 41.66°, -91.53°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
9.5°C
Average daily high
14.4°C
Average daily low
4.8°C
Annual rainfall
940mm
Sunshine / day
8.8h
Mean relative humidity
71%
Average peak wind
21.1km/h
Seasonal range
30.2°C
Frost days (< 0 °C)
127 d/yr
Hot days (≥ 30 °C)
27 d/yr
Rainy days (≥ 1 mm)
108 d/yr
Annual snowfall
67.7 cm
Average feels-like high
12.3 °C
Average feels-like low
1.6 °C
Average peak gust
39.1 km/h
Tropical nights (≥ 20 °C)
28 d/yr
Solar radiation
15.2 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.9 °C
since 1940
+0.2 °C per decade · r² = 0.30 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
39.6 °C
16 August 1988
Coldest day
-34.9 °C
16 January 2009
Wettest day
131 mm
13 September 1961
Windiest day
63.9 km/h
15 March 1959
Strongest gust
106.6 km/h
5 May 1950
Hottest feels-like
44.6 °C
6 July 1948
Coldest feels-like
-40.6 °C
16 January 2009
Snowiest day
32.8 cm
5 March 1959
Sunniest day
14.6 h
29 June 1940
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | -1.0 °C | +1.5 °C | 18 mm | -22 mm |
| Feb | 0.1 °C | 0.0 °C | 14 mm | -25 mm |
| Mar | 13.5 °C | +6.2 °C | 101 mm | +27 mm |
| Apr | 16.7 °C | +1.5 °C | 119 mm | +15 mm |
| May | 22.1 °C | +0.8 °C | 89 mm | -26 mm |
| Jun | 28.1 °C | +1.7 °C | 120 mm | +4 mm |
| Jul | 28.8 °C | +0.5 °C | 199 mm | +105 mm |
| Aug | 26.8 °C | -0.6 °C | 92 mm | -4 mm |
| Sep | 26.6 °C | +3.0 °C | 30 mm | -58 mm |
| Oct | 20.2 °C | +3.0 °C | 50 mm | -22 mm |
| Nov | 9.9 °C | +1.6 °C | 45 mm | -12 mm |
| Dec | -0.1 °C | -0.7 °C | 37 mm | -9 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Iowa City?
Iowa City has a hot-summer humid continental climate (Köppen Dfa). Over 1940-2025, the average annual temperature is 9.5 °C and it receives 940 mm of precipitation per year.
What is the hottest day ever recorded in Iowa City?
The hottest day measured in Iowa City between 1940 and 2025 was 16 August 1988, reaching 39.6 °C.
What is the coldest day in Iowa City?
The coldest day measured in Iowa City between 1940 and 2025 was 16 January 2009, at -34.9 °C.
Does it snow in Iowa City?
Yes. Iowa City gets on average 67.7 cm of snow per year and has around 127 frost days.
Has the climate of Iowa City warmed?
Yes: Iowa City warmed by +1.9 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Iowa City?
The wettest day measured in Iowa City between 1940 and 2025 was 13 September 1961, with 131 mm of rain in 24 hours.
What was the windiest day in Iowa City?
The windiest day measured in Iowa City between 1940 and 2025 was 15 March 1959, with winds reaching 63.9 km/h.
What is the warmest month in Iowa City?
The warmest month in Iowa City is July (23.4 °C on average); the coldest is January (-6.8 °C).
How much does it rain in Iowa City?
Iowa City receives on average 940 mm of precipitation per year, spread over about 108 rainy days.
Is it sunny in Iowa City?
Iowa City gets on average 8.8 hours of sunshine per day, roughly 3,212 hours per year over 1940-2025.
What is the biggest single-day snowfall in Iowa City?
The heaviest 24-hour snowfall measured in Iowa City between 1940 and 2025 was 5 March 1959, with 32.8 cm.
Are there tropical nights in Iowa City?
Yes: Iowa City has on average 28 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Iowa City?
In Iowa City, between 1940 and 2025, the highest apparent temperature reached 44.6 °C on 6 July 1948, and the lowest was -40.6 °C on 16 January 2009.
Compare Iowa City with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Iowa City