Rathbun, Iowa climate: Normal weather by month, frost dates and records
Rathbun's normal year runs from 13°F January nights to 85°F July afternoons, with 38.6 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.2°C, January lows of −11°C, July highs of 29°C, 980 mm of precipitation a year.
- NOAA stationRathbun Dam
- Station IDUSC00136910
- Location40.83°N 92.89°W
- Elevation965 ft (294 m)
- Population44
On October 14, the normal high in Rathbun is 66°F and the normal low 43°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Rathbun.
- Jan 31° 13°
- Feb 37° 16°
- Mar 50° 28°
- Apr 62° 39°
- May 71° 51°
- Jun 81° 61°
- Jul 85° 66°
- Aug 84° 64°
- Sep 77° 54°
- Oct 65° 42°
- Nov 50° 29°
- Dec 37° 19°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Rathbun each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 13°F. The most precipitation falls in May (5.36 in), the least in January (1.09 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 31°F | 13°F | 22.0°F | 1.09 | – | <1 | 30 | 9 h 30 min |
| February | 37°F | 16°F | 26.1°F | 1.49 | – | <1 | 26 | 10 h 40 min |
| March | 50°F | 28°F | 38.8°F | 2.03 | – | <1 | 21 | 11 h 50 min |
| April | 62°F | 39°F | 50.3°F | 3.93 | – | <1 | 6 | 13 h 20 min |
| May | 71°F | 51°F | 61.4°F | 5.36 | – | <1 | <1 | 14 h 30 min |
| June | 81°F | 61°F | 71.2°F | 5.24 | – | 3 | <1 | 15 h |
| July | 85°F | 66°F | 75.3°F | 4.57 | – | 8 | <1 | 14 h 50 min |
| August | 84°F | 64°F | 73.5°F | 4.62 | – | 6 | <1 | 13 h 50 min |
| September | 77°F | 54°F | 65.2°F | 3.81 | – | 2 | <1 | 12 h 30 min |
| October | 65°F | 42°F | 53.3°F | 2.93 | – | <1 | 5 | 11 h 10 min |
| November | 50°F | 29°F | 39.6°F | 2.04 | – | <1 | 19 | 10 h |
| December | 37°F | 19°F | 28.2°F | 1.46 | – | <1 | 28 | 9 h 20 min |
| Year (annual) | 61°F | 40°F | 50.4°F | 38.57 | – | 19 | 136 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 0°C | −11°C | −5.6°C | 28 mm |
| February | 3°C | −9°C | −3.3°C | 38 mm |
| March | 10°C | −2°C | 3.8°C | 52 mm |
| April | 17°C | 4°C | 10.2°C | 100 mm |
| May | 22°C | 11°C | 16.3°C | 136 mm |
| June | 27°C | 16°C | 21.8°C | 133 mm |
| July | 29°C | 19°C | 24.1°C | 116 mm |
| August | 29°C | 18°C | 23.1°C | 117 mm |
| September | 25°C | 12°C | 18.4°C | 97 mm |
| October | 18°C | 6°C | 11.8°C | 74 mm |
| November | 10°C | −1°C | 4.2°C | 52 mm |
| December | 3°C | −7°C | −2.1°C | 37 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Centerville (6 miles away), gets 22 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136910; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Rathbun?
Normal highs sit between 65°F and 85°F in May, June, July, August and September.
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136910.
When is the last frost in Rathbun?
In Rathbun, the last spring frost (32°F) comes after April 18 in half of years and after May 2 in one year in ten; the first autumn frost comes before October 23 in half of years and before October 10 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 181 year in 10 after May 2; 9 in 10 after April 4
- First autumn frost, half of years before
- October 231 year in 10 before October 10; 9 in 10 before November 1
NOAA puts the median frost-free season at 187 days, and the season without a hard freeze (28°F) at 206 days.
A hard freeze (28°F) comes after April 7 in half of springs and before October 31 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Rathbun in zone 5b in ZIP code 52574, the nearest ZIP area.
Frost dates for every NOAA station in Iowa · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00136910; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Rathbun?
In a normal year in Rathbun, 19 days a year reach 90°F (1 of them 100°F or more) and 136 nights fall to 32°F or colder.
- Days at 90°F or more
- 19a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 136a normal year
- Days that stay below freezing
- 42high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00136910.
How sunny is Rathbun?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Rathbun, 4.1 kWh per square metre a day. September is the sunniest month (82%) and January the cloudiest (65%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 65% | 1.9 |
| February | 69% | 2.9 |
| March | 68% | 3.8 |
| April | 70% | 4.9 |
| May | 72% | 5.6 |
| June | 78% | 6.3 |
| July | 82% | 6.4 |
| August | 80% | 5.5 |
| September | 82% | 4.7 |
| October | 73% | 3.2 |
| November | 72% | 2.2 |
| December | 66% | 1.7 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Rathbun need?
A normal year in Rathbun brings 6,263 heating degree days, 17% more than the median U.S. place (5,373), and 976 cooling degree days, 8% more than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,337 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,333 | 0 |
| February | 1,089 | 0 |
| March | 815 | 1 |
| April | 449 | 6 |
| May | 171 | 58 |
| June | 19 | 203 |
| July | 2 | 321 |
| August | 6 | 270 |
| September | 95 | 101 |
| October | 378 | 15 |
| November | 764 | 0 |
| December | 1,142 | 0 |
| Year (annual) | 6,263 | 976 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136910. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
How does Rathbun's climate compare?
Rathbun is warmer than 115 of the other 131 places with their own NOAA record in Iowa, and wetter than 103. Across the 7,247 U.S. stations with normals, its annual mean of 50.4°F is warmer than 42%.
In the Köppen classification computed from these normals, Rathbun is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Rathbun share this climate record?
3 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Moravia, IA625 people · 6 mi NE
- Mystic, IA318 people · 4 mi SW
- Unionville, IA74 people · 10 mi E
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Rathbun's climate
What is the coldest month in Rathbun?
January, with a normal high of 31°F and a normal low of 13°F. The warmest is July (85°F by day, 66°F at night).
Does it snow in Rathbun?
Yes. NOAA publishes no 1991-2020 snowfall normal for Rathbun's NOAA station; the nearest record that keeps one, Centerville (6 miles away), records 22 inches of snow in a normal year.
What is the rainiest month in Rathbun?
May, with 5.36 in of precipitation in a normal year; the driest is January with 1.09 in.
What plant hardiness zone is Rathbun in?
The USDA's 2023 map puts Rathbun in zone 5b in ZIP code 52574, the nearest ZIP area.
How late can frost come in Rathbun?
In half of years the last 32°F night comes after April 18; in one year in ten it comes after May 2. Waiting until May 2 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Centerville, IA6 miles from this station, 49.9°F a year
- Albia, IA17 miles from this station, 50.0°F a year
- Chariton, IA24 miles from this station, 48.3°F a year
- Unionville, MO25 miles from this station, 50.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made