Waterloo climate — normals and trends
Waterloo (United States) has a hot-summer humid continental climate (Dfa) under the Köppen-Geiger classification. Its mean annual temperature is 8.6 °C and it receives 929 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 (22.8 °C on average) and the coldest is January (-8.2 °C). Rainfall peaks in May.
Waterloo averages 137 frost days, 22 hot days (≥ 30 °C) and 109 rainy days per year.
Waterloo has warmed by +2.0 °C between 1940 and 2025, or +0.23 °C per decade. This trend is statistically significant.
The number of frost days there went from about 145 to 129 per year over the period.
The hottest day of the period reached 39.1 °C (on 17 August 1988) and the coldest -35.6 °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
WaterlooIowa
- coords
- 42.49°, -92.34°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
8.6°C
Average daily high
13.5°C
Average daily low
3.7°C
Annual rainfall
929mm
Sunshine / day
8.9h
Mean relative humidity
71%
Average peak wind
22.0km/h
Seasonal range
31.0°C
Frost days (< 0 °C)
137 d/yr
Hot days (≥ 30 °C)
22 d/yr
Rainy days (≥ 1 mm)
109 d/yr
Annual snowfall
75.6 cm
Average feels-like high
11.1 °C
Average feels-like low
0.4 °C
Average peak gust
40.1 km/h
Tropical nights (≥ 20 °C)
20 d/yr
Solar radiation
15.0 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+2.0 °C
since 1940
+0.2 °C per decade · r² = 0.31 · 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
39.1 °C
17 August 1988
Coldest day
-35.6 °C
16 January 2009
Wettest day
113 mm
10 September 1986
Windiest day
71.7 km/h
16 March 1941
Strongest gust
113.0 km/h
10 November 1998
Hottest feels-like
46.1 °C
6 July 1948
Coldest feels-like
-42.0 °C
2 February 1996
Snowiest day
28.9 cm
9 April 1973
Sunniest day
14.8 h
25 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 | -1.6 °C | +2.4 °C | 4 mm | -30 mm |
| Feb | -1.7 °C | -0.4 °C | 15 mm | -19 mm |
| Mar | 12.8 °C | +6.9 °C | 104 mm | +33 mm |
| Apr | 15.8 °C | +1.3 °C | 143 mm | +38 mm |
| May | 21.7 °C | +0.8 °C | 59 mm | -62 mm |
| Jun | 27.7 °C | +1.8 °C | 144 mm | +24 mm |
| Jul | 27.9 °C | +0.2 °C | 238 mm | +137 mm |
| Aug | 26.1 °C | -0.6 °C | 52 mm | -46 mm |
| Sep | 25.8 °C | +2.9 °C | 35 mm | -52 mm |
| Oct | 19.1 °C | +2.6 °C | 51 mm | -16 mm |
| Nov | 8.9 °C | +1.7 °C | 40 mm | -13 mm |
| Dec | -1.5 °C | -0.8 °C | 30 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 Waterloo?
Waterloo has a hot-summer humid continental climate (Köppen Dfa). Over 1940-2025, the average annual temperature is 8.6 °C and it receives 929 mm of precipitation per year.
What is the hottest day ever recorded in Waterloo?
The hottest day measured in Waterloo between 1940 and 2025 was 17 August 1988, reaching 39.1 °C.
What is the coldest day in Waterloo?
The coldest day measured in Waterloo between 1940 and 2025 was 16 January 2009, at -35.6 °C.
Does it snow in Waterloo?
Yes. Waterloo gets on average 75.6 cm of snow per year and has around 137 frost days.
Has the climate of Waterloo warmed?
Yes: Waterloo warmed by +2.0 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Waterloo?
The wettest day measured in Waterloo between 1940 and 2025 was 10 September 1986, with 113 mm of rain in 24 hours.
What was the windiest day in Waterloo?
The windiest day measured in Waterloo between 1940 and 2025 was 16 March 1941, with winds reaching 71.7 km/h.
What is the warmest month in Waterloo?
The warmest month in Waterloo is July (22.8 °C on average); the coldest is January (-8.2 °C).
How much does it rain in Waterloo?
Waterloo receives on average 929 mm of precipitation per year, spread over about 109 rainy days.
Is it sunny in Waterloo?
Waterloo gets on average 8.9 hours of sunshine per day, roughly 3,249 hours per year over 1940-2025.
What is the biggest single-day snowfall in Waterloo?
The heaviest 24-hour snowfall measured in Waterloo between 1940 and 2025 was 9 April 1973, with 28.9 cm.
Are there tropical nights in Waterloo?
Yes: Waterloo has on average 20 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Waterloo?
In Waterloo, between 1940 and 2025, the highest apparent temperature reached 46.1 °C on 6 July 1948, and the lowest was -42.0 °C on 2 February 1996.
Compare Waterloo with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Waterloo