Mason City climate — normals and trends
Mason City (United States) has a hot-summer humid continental climate (Dfa) under the Köppen-Geiger classification. Its mean annual temperature is 7.6 °C and it receives 895 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 (22.3 °C on average) and the coldest is January (-9.5 °C). Rainfall peaks in June.
Mason City averages 146 frost days, 18 hot days (≥ 30 °C) and 108 rainy days per year.
Mason City has warmed by +2.1 °C between 1940 and 2025, or +0.25 °C per decade. This trend is statistically significant.
The number of frost days there went from about 153 to 139 per year over the period.
The hottest day of the period reached 39.5 °C (on 31 July 1988) and the coldest -35.9 °C (on 2 February 1996).
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
Mason CityIowa
- coords
- 43.15°, -93.20°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
7.6°C
Average daily high
12.5°C
Average daily low
2.9°C
Annual rainfall
895mm
Sunshine / day
8.8h
Mean relative humidity
72%
Average peak wind
23.3km/h
Seasonal range
31.8°C
Frost days (< 0 °C)
146 d/yr
Hot days (≥ 30 °C)
18 d/yr
Rainy days (≥ 1 mm)
108 d/yr
Annual snowfall
85.9 cm
Average feels-like high
9.8 °C
Average feels-like low
-0.7 °C
Average peak gust
41.6 km/h
Tropical nights (≥ 20 °C)
16 d/yr
Solar radiation
14.9 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+2.1 °C
since 1940
+0.3 °C per decade · r² = 0.32 · 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
39.5 °C
31 July 1988
Coldest day
-35.9 °C
2 February 1996
Wettest day
76 mm
28 August 2015
Windiest day
75.1 km/h
10 October 1949
Strongest gust
121.7 km/h
10 October 1949
Hottest feels-like
45.5 °C
6 July 1948
Coldest feels-like
-43.9 °C
10 January 1982
Snowiest day
25.4 cm
18 November 1957
Sunniest day
14.9 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 | -2.7 °C | +2.6 °C | 1 mm | -27 mm |
| Feb | -2.8 °C | -0.1 °C | 17 mm | -13 mm |
| Mar | 11.0 °C | +6.7 °C | 114 mm | +48 mm |
| Apr | 15.0 °C | +1.4 °C | 143 mm | +46 mm |
| May | 21.0 °C | +0.7 °C | 74 mm | -46 mm |
| Jun | 26.6 °C | +1.3 °C | 186 mm | +61 mm |
| Jul | 27.4 °C | +0.2 °C | 174 mm | +77 mm |
| Aug | 25.4 °C | -0.7 °C | 98 mm | -2 mm |
| Sep | 24.4 °C | +2.3 °C | 51 mm | -35 mm |
| Oct | 17.4 °C | +1.8 °C | 50 mm | -14 mm |
| Nov | 8.0 °C | +2.1 °C | 49 mm | +1 mm |
| Dec | -1.8 °C | +0.3 °C | 33 mm | -2 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 Mason City?
Mason City has a hot-summer humid continental climate (Köppen Dfa). Over 1940-2025, the average annual temperature is 7.6 °C and it receives 895 mm of precipitation per year.
What is the hottest day ever recorded in Mason City?
The hottest day measured in Mason City between 1940 and 2025 was 31 July 1988, reaching 39.5 °C.
What is the coldest day in Mason City?
The coldest day measured in Mason City between 1940 and 2025 was 2 February 1996, at -35.9 °C.
Does it snow in Mason City?
Yes. Mason City gets on average 85.9 cm of snow per year and has around 146 frost days.
Has the climate of Mason City warmed?
Yes: Mason City warmed by +2.1 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Mason City?
The wettest day measured in Mason City between 1940 and 2025 was 28 August 2015, with 76 mm of rain in 24 hours.
What was the windiest day in Mason City?
The windiest day measured in Mason City between 1940 and 2025 was 10 October 1949, with winds reaching 75.1 km/h.
What is the warmest month in Mason City?
The warmest month in Mason City is July (22.3 °C on average); the coldest is January (-9.5 °C).
How much does it rain in Mason City?
Mason City receives on average 895 mm of precipitation per year, spread over about 108 rainy days.
Is it sunny in Mason City?
Mason 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 Mason City?
The heaviest 24-hour snowfall measured in Mason City between 1940 and 2025 was 18 November 1957, with 25.4 cm.
Are there tropical nights in Mason City?
Yes: Mason City has on average 16 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Mason City?
In Mason City, between 1940 and 2025, the highest apparent temperature reached 45.5 °C on 6 July 1948, and the lowest was -43.9 °C on 10 January 1982.
Compare Mason City with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Mason City