Mason City weather in December: Mason City, Iowa: normal highs, lows, rain and records for December
Mason City in December has a normal high of 30°F and a normal low of 14°F, a daily mean of 22°F, falling from 36°F on the 1st to 25°F by the 31st. Measurable precipitation falls on 8 days in a normal December, 1.29 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of −1°C and low of −10°C, 33 mm of precipitation and 24 cm of snow in December.
- NOAA stationMason City Municipal Airport
- Station IDUSW00014940
- Location43.15°N 93.33°W
- Elevation1,225 ft (373 m)
- From the center6 miles
- Population26,948
- Jan 24° 7°
- Feb 29° 11°
- Mar 42° 24°
- Apr 58° 35°
- May 70° 47°
- Jun 80° 57°
- Jul 83° 61°
- Aug 80° 58°
- Sep 74° 49°
- Oct 60° 37°
- Nov 44° 24°
- Dec 30° 14°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Mason City in December?
The normal high is 30°F and the normal low 14°F, for a daily mean of 21.6°F. December is 12.3°F cooler than November and 5.9°F warmer than January. December is the 10th warmest month of the year in Mason City and the 10th wettest. Across the month the normal high falls 11°F, from 36°F on December 1 to 25°F on December 31. From one year to the next December's mean temperature typically moves about 5.4°F either way (NOAA's standard deviation), so roughly two Decembers in three average between 16°F and 27°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 27%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| December 1 | 36°F | 18°F | 27% | 13% |
| December 8 | 32°F | 16°F | 27% | 12% |
| December 15 | 30°F | 14°F | 27% | 11% |
| December 22 | 27°F | 12°F | 26% | 11% |
| December 31 | 25°F | 9°F | 26% | 11% |
Every day of December: normal high, low and chance of precipitation (warmest afternoon December 1, coldest night December 31)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| December 1 | 36°F | 18°F | 27% | 13% | 9 h 20 min |
| December 2 | 35°F | 18°F | 27% | 12% | 9 h 10 min |
| December 3 | 35°F | 18°F | 27% | 12% | 9 h 10 min |
| December 4 | 34°F | 17°F | 27% | 12% | 9 h 10 min |
| December 5 | 34°F | 17°F | 27% | 12% | 9 h 10 min |
| December 6 | 33°F | 17°F | 27% | 12% | 9 h 10 min |
| December 7 | 33°F | 16°F | 27% | 12% | 9 h 10 min |
| December 8 | 32°F | 16°F | 27% | 12% | 9 h 10 min |
| December 9 | 32°F | 16°F | 27% | 12% | 9 h 10 min |
| December 10 | 32°F | 15°F | 27% | 12% | 9 h |
| December 11 | 31°F | 15°F | 27% | 12% | 9 h |
| December 12 | 31°F | 15°F | 27% | 12% | 9 h |
| December 13 | 30°F | 14°F | 27% | 11% | 9 h |
| December 14 | 30°F | 14°F | 27% | 11% | 9 h |
| December 15 | 30°F | 14°F | 27% | 11% | 9 h |
| December 16 | 29°F | 13°F | 26% | 11% | 9 h |
| December 17 | 29°F | 13°F | 26% | 11% | 9 h |
| December 18 | 29°F | 13°F | 26% | 11% | 9 h |
| December 19 | 28°F | 13°F | 26% | 11% | 9 h |
| December 20 | 28°F | 12°F | 26% | 11% | 9 h |
| December 21 | 28°F | 12°F | 26% | 11% | 9 h |
| December 22 | 27°F | 12°F | 26% | 11% | 9 h |
| December 23 | 27°F | 11°F | 26% | 11% | 9 h |
| December 24 | 27°F | 11°F | 26% | 11% | 9 h |
| December 25 | 27°F | 11°F | 26% | 11% | 9 h |
| December 26 | 26°F | 11°F | 26% | 11% | 9 h |
| December 27 | 26°F | 10°F | 26% | 11% | 9 h |
| December 28 | 26°F | 10°F | 26% | 11% | 9 h |
| December 29 | 26°F | 10°F | 26% | 11% | 9 h |
| December 30 | 26°F | 10°F | 26% | 11% | 9 h |
| December 31 | 25°F | 9°F | 26% | 11% | 9 h |
- Normal high
- 30°FDecember average
- Normal low
- 14°FDecember average
- Precipitation
- 1.29 inmonth total
- Days with precipitation
- 80.01 inch or more
- Snowfall
- 9.4 inmonth total
- Nights at 32°F or colder
- 30
- Daylight
- 9 h 20 min to 9 hDecember 1 to December 31
- Sunshine
- 65%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00014940; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain or snow in Mason City in December?
On a given December day the chance of 0.01 inch or more is 27% on average, highest around December 3 (27%). In all, 1.29 in falls on 8 days of a normal December.
In a normal December in Mason City, 30 nights fall to freezing, 17 days stay below freezing all day and snowfall averages 9.4 inches.
Snow falls on 7 days in a normal December, and an inch or more covers the ground on 16 days.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00014940.
How humid and windy is Mason City in December?
At 3 p.m. the normal temperature is 23°F with 74% relative humidity and a dew point of 16°F; at 6 a.m. it is 15°F with 84% humidity. The wind averages 12.1 mph, most often from the west-northwest in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 15°F | 11°F | 84% | 11.4 mph | 54% |
| 9 a.m. | 16°F | 12°F | 83% | 12.0 mph | 47% |
| noon | 21°F | 15°F | 76% | 13.4 mph | 45% |
| 3 p.m. | 23°F | 16°F | 74% | 13.5 mph | 46% |
| 6 p.m. | 20°F | 15°F | 81% | 11.4 mph | – |
| 9 p.m. | 18°F | 14°F | 82% | 11.6 mph | 53% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014940. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for December in Mason City?
The warmest December temperature on this station's record (since 1948) is 69°F, on December 15, 2021; the coldest is −26°F, on December 27, 1950. The wettest December brought 3.95 in (1982); the snowiest, 27.6 inches (1969).
The December mean against the 1991-2020 normal of 21.6°F: 2021 27.1°F (+5.4), 2022 17.6°F (−4.0), 2023 31.1°F (+9.4), 2024 25.7°F (+4.1), 2025 19.4°F (−2.2). 3 of 5 ran warmer than normal.
| December | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 27.1°F | +5.4°F | 0.91 in |
| 2022 | 17.6°F | −4.0°F | 1.24 in |
| 2023 | 31.1°F | +9.4°F | 1.27 in |
| 2024 | 25.7°F | +4.1°F | 1.12 in |
| 2025 | 19.4°F | −2.2°F | 0.51 in |
Source: records: ACIS, station USW00014940; recent months: ACIS, station USW00014940. Records and recent months use complete months only.
How does December in Mason City compare across Iowa?
Across the 132 places PlainClimate covers in Iowa, December normal highs run from 27°F in Northwood to 38°F in Keokuk; Mason City's is 30°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.