Red Oak, Iowa climate: Normal weather by month, frost dates and records
Red Oak's normal year runs from 13°F January nights to 86°F July afternoons, with 37.2 inches of precipitation and 27 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.4°C, January lows of −11°C, July highs of 30°C, 946 mm of precipitation a year.
- NOAA stationRed Oak
- Station IDUSC00136940
- Location41.00°N 95.24°W
- Elevation1,040 ft (317 m)
- From the center1 miles
- Population5,420
On October 23, the normal high in Red Oak is 62°F and the normal low 38°F, and the chance of measurable rain or snow is 24%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Red Oak.
- Jan 33° 13°
- Feb 38° 16°
- Mar 51° 28°
- Apr 63° 38°
- May 73° 51°
- Jun 83° 61°
- Jul 86° 66°
- Aug 85° 63°
- Sep 78° 53°
- Oct 66° 41°
- Nov 50° 28°
- Dec 37° 18°
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 Red Oak each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 13°F. The most precipitation falls in May (5.95 in), the least in January (0.88 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 33°F | 13°F | 22.7°F | 0.88 | 7.3 | 5 | <1 | 30 | 9 h 30 min |
| February | 38°F | 16°F | 27.1°F | 1.11 | 8.1 | 7 | <1 | 26 | 10 h 40 min |
| March | 51°F | 28°F | 39.3°F | 2.03 | 2.6 | 8 | <1 | 21 | 11 h 50 min |
| April | 63°F | 38°F | 50.7°F | 3.83 | 1.2 | 11 | <1 | 8 | 13 h 20 min |
| May | 73°F | 51°F | 62.1°F | 5.95 | 0.0 | 14 | 1 | 1 | 14 h 30 min |
| June | 83°F | 61°F | 72.1°F | 5.44 | 0.0 | 11 | 5 | <1 | 15 h 10 min |
| July | 86°F | 66°F | 75.9°F | 3.96 | 0.0 | 10 | 10 | <1 | 14 h 50 min |
| August | 85°F | 63°F | 73.7°F | 3.89 | 0.0 | 9 | 7 | <1 | 13 h 50 min |
| September | 78°F | 53°F | 65.8°F | 3.58 | 0.0 | 8 | 3 | <1 | 12 h 30 min |
| October | 66°F | 41°F | 53.2°F | 3.31 | 0.5 | 8 | <1 | 7 | 11 h 10 min |
| November | 50°F | 28°F | 39.1°F | 1.88 | 1.2 | 6 | <1 | 20 | 10 h |
| December | 37°F | 18°F | 27.6°F | 1.38 | 6.5 | 6 | <1 | 29 | 9 h 20 min |
| Year (annual) | 62°F | 40°F | 50.8°F | 37.24 | 27.4 | 102 | 26 | 142 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 0°C | −11°C | −5.2°C | 22 mm | 19 cm |
| February | 3°C | −9°C | −2.7°C | 28 mm | 21 cm |
| March | 11°C | −2°C | 4.1°C | 52 mm | 7 cm |
| April | 17°C | 3°C | 10.4°C | 97 mm | 3 cm |
| May | 23°C | 10°C | 16.7°C | 151 mm | 0 cm |
| June | 28°C | 16°C | 22.3°C | 138 mm | 0 cm |
| July | 30°C | 19°C | 24.4°C | 101 mm | 0 cm |
| August | 29°C | 17°C | 23.2°C | 99 mm | 0 cm |
| September | 26°C | 12°C | 18.8°C | 91 mm | 0 cm |
| October | 19°C | 5°C | 11.8°C | 84 mm | 1 cm |
| November | 10°C | −2°C | 3.9°C | 48 mm | 3 cm |
| December | 3°C | −8°C | −2.4°C | 35 mm | 17 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136940; 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 Red Oak?
Normal highs sit between 65°F and 85°F in May, June, August, September and October. Of those, September has the fewest days with rain (8).
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 USC00136940.
When is the last frost in Red Oak?
In Red Oak, the last spring frost (32°F) comes after April 24 in half of years and after May 8 in one year in ten; the first autumn frost comes before October 13 in half of years and before September 26 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 241 year in 10 after May 8; 9 in 10 after April 10
- First autumn frost, half of years before
- October 131 year in 10 before September 26; 9 in 10 before October 25
NOAA puts the median frost-free season at 169 days, and the season without a hard freeze (28°F) at 190 days.
A hard freeze (28°F) comes after April 15 in half of springs and before October 23 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Red Oak in zone 5b in ZIP code 51566, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Red Oak's NOAA station is in zone 5b: the coldest night of a typical year reaches −14°F (28 complete years).
Frost dates for every NOAA station in Iowa · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00136940; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. 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 Red Oak?
In a normal year in Red Oak, 26 days a year reach 90°F (1 of them 100°F or more), 142 nights fall to 32°F or colder and 102 days bring measurable precipitation.
- Days at 90°F or more
- 26a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 142a normal year
- Days that stay below freezing
- 41high of 32°F or less
- Days with 0.01 inch of precipitation
- 102a normal year
- Days with 1 inch of snow or more
- 9a normal year
The highest temperature in this station's record (since 1897) is 109°F, on July 21, 1974; the lowest is −28°F, on February 3, 1996.
The wettest calendar year on that record is 2007, with 56.24 in; the snowiest season is 1935–36, with 60.9 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00136940; records: ACIS (NOAA Regional Climate Centers), station USC00136940. Records use complete months only; a month missing more than three days is left out.
How sunny is Red Oak?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Red Oak, 4.2 kWh per square metre a day. July is the sunniest month (83%) and December the cloudiest (69%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 69% | 2.0 |
| February | 74% | 3.0 |
| March | 69% | 3.8 |
| April | 70% | 4.9 |
| May | 73% | 5.8 |
| June | 79% | 6.5 |
| July | 83% | 6.5 |
| August | 81% | 5.6 |
| September | 81% | 4.6 |
| October | 75% | 3.2 |
| November | 74% | 2.3 |
| December | 69% | 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 Red Oak need?
A normal year in Red Oak brings 6,205 heating degree days, 15% more than the median U.S. place (5,373), and 1,057 cooling degree days, 17% 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 3,441 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,313 | 0 |
| February | 1,061 | 0 |
| March | 798 | 2 |
| April | 437 | 9 |
| May | 161 | 71 |
| June | 16 | 229 |
| July | 2 | 340 |
| August | 6 | 275 |
| September | 92 | 116 |
| October | 383 | 16 |
| November | 779 | 0 |
| December | 1,158 | 0 |
| Year (annual) | 6,205 | 1,057 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136940. 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.
Has Red Oak been warmer than normal lately?
2023 averaged 52.5°F, 1.7°F above the 1991-2020 normal of 50.8°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 51.9°F | +1.1°F | 35.46 | 26.1 |
| 2022 | 49.7°F | −1.1°F | 22.38 | 9.8 |
| 2023 | 52.5°F | +1.7°F | 22.74 | 9.5 |
Over 66 complete years from 1941 to 2024, the station's annual mean temperature rose at a fitted 4.2°F per century (+0.24°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00136940; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Red Oak's climate compare?
Red Oak is warmer than 121 of the other 131 places with their own NOAA record in Iowa, and wetter than 75. Across the 7,247 U.S. stations with normals, its annual mean of 50.8°F is warmer than 44%.
In the Köppen classification computed from these normals, Red Oak 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 Red Oak share this climate record?
5 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.
- Stanton, IA664 people · 7 mi E
- Emerson, IA401 people · 8 mi W
- Elliott, IA328 people · 11 mi N
- Hastings, IA157 people · 13 mi W
- Coburg, IA26 people · 6 mi S
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 Red Oak's climate
What is the coldest month in Red Oak?
January, with a normal high of 33°F and a normal low of 13°F. The warmest is July (86°F by day, 66°F at night).
Does it snow in Red Oak?
Yes: 27 inches in a normal year, falling on 15 days with 0.1 inch or more, the most in February (8.1 inches).
What is the rainiest month in Red Oak?
May, with 5.95 in of precipitation in a normal year; the driest is January with 0.88 in.
What plant hardiness zone is Red Oak in?
The USDA's 2023 map puts Red Oak in zone 5b in ZIP code 51566, the nearest ZIP area. By the same method at Red Oak's NOAA station, the coldest night of a typical year reaches −14°F (28 years, 1991-2020): zone 5b.
How late can frost come in Red Oak?
In half of years the last 32°F night comes after April 24; in one year in ten it comes after May 8. Waiting until May 8 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Shenandoah, IA17 miles from this station, 51.8°F a year
- Oakland, IA22 miles from this station, 49.4°F a year
- Clarinda, IA22 miles from this station, 50.3°F a year
- Corning, IA25 miles from this station, 49.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made