Mason City, IL Climate: Temperature & Rain by Month
Temperature and precipitation from NOAA NCEI 1991–2020 normals →, plus PlainClimate's derived comfort score
30-year climate normals (1991-2020) from Mason City's primary NOAA station, MASON CITY 4SE.
The climate verdict for Mason City
Mason City, Illinois has a mixed annual climate rather than one dominant extreme. Its NOAA normal shows an annual average of 52°F. Its climate comfort score of 68/100 (good) lands mid-pack nationally, exceeding 56% of station-mapped location scores.
- 52°F
- average temperature, NOAA 1991-2020 normal
- 68/100
- comfort score, above 56% of station-mapped location scores
- 39.3"
- annual precipitation · 13" snow
- 184 days
- growing season, frost-free days
Mason City: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00115413 · Mason City, IL 52°F mean · 39.3" precip
TEMP-COOL · RANK-MID · PHOTO-FINISH · PRCP-MID · SWING-WIDE · COMF-MID · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 52°F
- RANK-MID #3,293
- PHOTO-FINISH ≈ Goodland
- PRCP-MID 39.3"
- SWING-WIDE 50°F
- COMF-MID 68/100
- LOAD-HEAT 5,821 HDD
- STN-1 USC00115413
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Goodland, KS (+ 0 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every IL station list.
- Mason City (this station) 52°F
- Cold Milford, UT 52°F
- Hot Rushville, IL 52°F
- Near Goodland, KS 52°F
- Near Eau Claire, MI 52°F
Climate Living Index · Mason City
Mason City: 59/100 · grade C
Mason City publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Mason City, not an official NOAA rating. Rankings still use Comfort Score 68/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Precipitation balance | 39.3 in · 4.3 from 35 in | 85/100 · A |
| Snowfall burden | 12.9 inches/year | 59/100 · C |
| Normal heat + freeze calendar | 133 calendar days | 57/100 · C |
| Frost-free season | 184 days/year | 53/100 · D |
| Annual temperature balance | 51.7°F · 15.8° from 67.5°F | 48/100 · D |
Mason City · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Mason City is a continental Köppen climate: Dfa
Coldest-month mean 24.6°F and warmest-month mean 74.9°F place this station in continental, no dry season, hot summer climates (Dfa). Class Dfa is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: continental, specifically continental, no dry season, hot summer.
- Köppen code
- Dfa
- Group
- Continental
- Warmest month
- 74.9°F
- Coldest month
- 24.6°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Mason City sits across the climate record
Three NOAA fields for Mason City's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 48th percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 56th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Wider than 82%
- Warmest-to-coldest month gap for Mason City is large versus 6,861 complete station-years.
How Mason City compares across U.S. station-mapped locations
Mason City's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
68 Top 44% score exceeds 56% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). This entry sits in this band.
- 70–80: 650 station-mapped locations (11%). Above this entry.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 33°F (1°C) | 16°F (-9°C) | 25°F (-4°C) | 2.3" | 5.5" | 28.4 | 0.0 |
| February | 38°F (3°C) | 19°F (-7°C) | 29°F (-2°C) | 2.0" | 2.8" | 23.7 | 0.0 |
| March | 51°F (10°C) | 30°F (-1°C) | 40°F (5°C) | 2.5" | 1.7" | 19.0 | 0.0 |
| April | 64°F (18°C) | 41°F (5°C) | 53°F (12°C) | 3.7" | 0.0" | 4.5 | 0.1 |
| May | 74°F (23°C) | 53°F (12°C) | 63°F (17°C) | 4.5" | 0.0" | 0.2 | 1.2 |
| June | 82°F (28°C) | 62°F (17°C) | 72°F (22°C) | 4.2" | 0.0" | 0.0 | 6.3 |
| July | 85°F (30°C) | 65°F (18°C) | 75°F (24°C) | 5.1" | 0.0" | 0.0 | 9.5 |
| August | 84°F (29°C) | 62°F (17°C) | 73°F (23°C) | 3.6" | 0.0" | 0.0 | 6.7 |
| September | 79°F (26°C) | 54°F (12°C) | 66°F (19°C) | 3.5" | 0.0" | 0.2 | 3.4 |
| October | 66°F (19°C) | 43°F (6°C) | 54°F (12°C) | 3.3" | 0.0" | 3.7 | 0.3 |
| November | 51°F (11°C) | 31°F (-1°C) | 41°F (5°C) | 2.8" | 0.3" | 16.5 | 0.0 |
| December | 38°F (3°C) | 22°F (-6°C) | 30°F (-1°C) | 1.7" | 2.6" | 25.7 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 86°F around July 7, short of 90°F on every date, while 133 dates carry a normal low at or below freezing, the coldest 15°F near January 21.
The freezing stretch
The normal low stays at or below 32°F into March 23, then returns to freezing around November 12, covering 133 dates in all.
Derived from the normal daily minimum. This is a different measure from the 50%-probability frost dates shown elsewhere on this page, which come from NOAA’s frost product.
Where the wet dates fall
The likeliest wet date is April 29, when 39% of years recorded at least a hundredth of an inch. The driest is December 24 at 21%. Summed across the calendar, that is about 101 wet dates a year.
The widest day
September 17 carries the biggest normal gap between afternoon and dawn, 25°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Mason City.
Monthly Precipitation
Average monthly rainfall and snowfall
Snow: 5.5"
7.6 days with precipitation
Snow: 2.8"
6.7 days with precipitation
Snow: 1.7"
7.9 days with precipitation
11.1 days with precipitation
10.9 days with precipitation
9.6 days with precipitation
8.7 days with precipitation
7.5 days with precipitation
7.2 days with precipitation
8.8 days with precipitation
Snow: 0.3"
6.9 days with precipitation
Snow: 2.6"
6.0 days with precipitation
Mason City spreads its precipitation across the year
Neither half of the year dominates here: June through August take 33% of the annual total and December through February 15%, with neither reaching the 35% that would mark a distinct wet season. Mason City has no dry season to plan around, though it does carry a wide 50.3°F gap between its warmest and coldest month.
The gap between the wettest and driest month still matters: July averages 5.1" and December 1.7". The three wettest months together take 35% of the year, against the 25% a perfectly flat distribution would give them.
Shares are computed from this station's own 1991-2020 monthly precipitation normals. "Spread across the year" means neither the June-August nor the December-February share reaches 35%; it describes an average year, not the variability of any single one.
When it rains in Mason City, it arrives in quantity
39.3" of precipitation falls across only about 99 wet days here, averaging 0.40 inches each. Fewer days carry more water: the year's total is delivered in comparatively heavy events rather than persistent damp.
- Days with measurable precipitation
- about 99 a year, 27% of all days
- Average depth per wet day
- 0.40 inches
- Most wet days
- April, about 11
- Fewest wet days
- December, about 6
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year, and a per-day average is not a forecast of any individual storm.
Winter brings real snow to Mason City
Mason City averages 12.9 inches of snowfall a year, with January the snowiest month on the normals, spread across roughly 11 days that record measurable snow. That is depth accumulating on the ground, which is why it can exceed the annual precipitation figure: precipitation counts the liquid the snow melts down to, and fresh snow is mostly air.
- Annual snowfall: 12.9 inches of depth.
- Days recording measurable snow: about 11 a year.
- At a rough ten-to-one melt ratio, snow accounts for on the order of 3% of the year's precipitation.
NOAA 1991-2020 normals. The ten-to-one ratio is a convention, not a measurement: real ratios vary with temperature, so treat the share as an order of magnitude rather than an exact split.
Frost Dates & Growing Season
First Fall Freeze
October 18
50% probability date
Last Spring Freeze
April 17
50% probability date
Growing Season
184 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
5,821
Higher = more heating needed
Cooling Degree Days
1,006
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Nationwide similar cities
Other rankable U.S. places outside IL closest to Mason City on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (52°F here).
- Burlington, CO 52°F · 0.0°F off
- Conception, MO 52°F · 0.0°F off
- Connell, WA 52°F · 0.0°F off
- Donnellson, IA 52°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (39.3" here), excluding temperature-peer places.
- Houlton, ME 39.3" · 0.0" off
- Newkirk, OK 39.3" · 0.0" off
- Cumberland, MD 39.2" · 0.0" off
- Kansas City, MO 39.3" · 0.0" off
Snow and freeze rhythm
When cold and snow define Mason City
heating led · moderate · mid swing
Mason City's energy balance leans toward cold weather: 5,821 annual heating degree days against 1,006 for cooling. Its 50.3°F seasonal range still makes the monthly rows more useful than the annual average alone.
Mason City's frost-free season lasts about 184 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
-
1. Mason City coldest normal
January
Averaging 25°F (-4°C), this month sits below freezing for the month as a whole, not merely overnight.
-
2. Mason City typical freeze period
January through December
The station reports average freezing days from January through December.
-
3. Mason City snow peak
January
Mason City averages 12.9 inches of snow a year, with January the snowiest month on the normals.
Questions about Mason City's climate
How much snow does Mason City get? ▼
How cold does Mason City get in winter? ▼
How much energy does heating and cooling require in Mason City? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Mason City's primary station: MASON CITY 4SE (USC00115413). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The 2024 Census Gazetteer identifies the exact name-and-state match as an incorporated place (GEOID 1747475). Match rule for Mason City: exact normalized name + state only, no fuzzy expansion, so nearby differently spelled facilities stay unmatched.
On this page every temperature, precipitation, and derived score for Mason City comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.