Oskaloosa, Iowa climate: Normal weather by month, frost dates and records
Oskaloosa's normal year runs from 12°F January nights to 86°F July afternoons, with 38.7 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.1°C, January lows of −11°C, July highs of 30°C, 983 mm of precipitation a year.
- NOAA stationOskaloosa
- Station IDUSC00136327
- Location41.32°N 92.65°W
- Elevation830 ft (253 m)
- From the center2 miles
- Population11,575
On October 23, the normal high in Oskaloosa is 61°F and the normal low 39°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 Oskaloosa.
- Jan 31° 12°
- Feb 36° 16°
- Mar 49° 27°
- Apr 62° 38°
- May 72° 51°
- Jun 82° 61°
- Jul 86° 65°
- Aug 84° 62°
- Sep 77° 53°
- Oct 65° 41°
- Nov 49° 29°
- Dec 36° 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 Oskaloosa each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 12°F. The most precipitation falls in June (5.18 in), the least in December (1.35 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 31°F | 12°F | 21.5°F | 1.75 | 6 | <1 | 30 | 9 h 30 min |
| February | 36°F | 16°F | 25.9°F | 1.74 | 6 | <1 | 26 | 10 h 40 min |
| March | 49°F | 27°F | 38.3°F | 2.15 | 7 | <1 | 22 | 11 h 50 min |
| April | 62°F | 38°F | 50.1°F | 3.92 | 10 | <1 | 9 | 13 h 20 min |
| May | 72°F | 51°F | 61.5°F | 4.71 | 12 | <1 | 1 | 14 h 30 min |
| June | 82°F | 61°F | 71.2°F | 5.18 | 10 | 2 | <1 | 15 h 10 min |
| July | 86°F | 65°F | 75.2°F | 4.40 | 9 | 8 | <1 | 14 h 50 min |
| August | 84°F | 62°F | 72.9°F | 5.08 | 9 | 4 | <1 | 13 h 50 min |
| September | 77°F | 53°F | 65.2°F | 3.56 | 7 | 2 | <1 | 12 h 30 min |
| October | 65°F | 41°F | 52.8°F | 2.68 | 7 | <1 | 7 | 11 h 10 min |
| November | 49°F | 29°F | 38.9°F | 2.20 | 6 | <1 | 20 | 9 h 50 min |
| December | 36°F | 18°F | 27.2°F | 1.35 | 6 | <1 | 29 | 9 h 10 min |
| Year (annual) | 61°F | 39°F | 50.1°F | 38.72 | 95 | 15 | 144 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −11°C | −5.8°C | 44 mm |
| February | 2°C | −9°C | −3.4°C | 44 mm |
| March | 10°C | −3°C | 3.5°C | 55 mm |
| April | 17°C | 3°C | 10.1°C | 100 mm |
| May | 22°C | 10°C | 16.4°C | 120 mm |
| June | 28°C | 16°C | 21.8°C | 132 mm |
| July | 30°C | 18°C | 24.0°C | 112 mm |
| August | 29°C | 17°C | 22.7°C | 129 mm |
| September | 25°C | 12°C | 18.4°C | 90 mm |
| October | 18°C | 5°C | 11.6°C | 68 mm |
| November | 10°C | −2°C | 3.8°C | 56 mm |
| December | 2°C | −8°C | −2.7°C | 34 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Ottumwa (18 miles away), gets 24 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136327; 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 Oskaloosa?
Normal highs sit between 65°F and 85°F in May, June, August and September. Of those, September has the fewest days with rain (7).
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 USC00136327.
When is the last frost in Oskaloosa?
In Oskaloosa, the last spring frost (32°F) comes after April 21 in half of years and after May 4 in one year in ten; the first autumn frost comes before October 16 in half of years and before September 29 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 211 year in 10 after May 4; 9 in 10 after April 8
- First autumn frost, half of years before
- October 161 year in 10 before September 29; 9 in 10 before October 29
NOAA puts the median frost-free season at 176 days, and the season without a hard freeze (28°F) at 198 days.
A hard freeze (28°F) comes after April 11 in half of springs and before October 27 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Oskaloosa in zone 5b in ZIP code 52595, 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 USC00136327; 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 Oskaloosa?
In a normal year in Oskaloosa, 15 days a year reach 90°F (1 of them 100°F or more), 144 nights fall to 32°F or colder and 95 days bring measurable precipitation.
- Days at 90°F or more
- 15a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 144a normal year
- Days that stay below freezing
- 46high of 32°F or less
- Days with 0.01 inch of precipitation
- 95a normal year
The highest temperature in this station's record (since 1893) is 112°F, on July 25, 1936; the lowest is −31°F, on January 12, 1912.
The wettest calendar year on that record is 1951, with 53.84 in; the snowiest season is 2007–08, with 70.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00136327; records: ACIS (NOAA Regional Climate Centers), station USC00136327. Records use complete months only; a month missing more than three days is left out.
How sunny is Oskaloosa?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Oskaloosa, 4.1 kWh per square metre a day. July is the sunniest month (81%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 69% | 2.0 |
| February | 74% | 3.0 |
| March | 70% | 3.8 |
| April | 70% | 4.8 |
| May | 72% | 5.6 |
| June | 77% | 6.2 |
| July | 81% | 6.3 |
| August | 80% | 5.5 |
| September | 81% | 4.6 |
| October | 73% | 3.1 |
| November | 71% | 2.1 |
| December | 66% | 1.6 |
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 Oskaloosa need?
A normal year in Oskaloosa brings 6,366 heating degree days, 18% more than the median U.S. place (5,373), and 958 cooling degree days, 6% 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 3,296 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,350 | 0 |
| February | 1,095 | 0 |
| March | 829 | 2 |
| April | 452 | 6 |
| May | 168 | 59 |
| June | 20 | 204 |
| July | 2 | 316 |
| August | 7 | 252 |
| September | 98 | 104 |
| October | 391 | 14 |
| November | 783 | 0 |
| December | 1,172 | 0 |
| Year (annual) | 6,366 | 958 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136327. 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 Oskaloosa been warmer than normal lately?
Over 90 complete years from 1893 to 2016, the station's annual mean temperature rose at a fitted 1.8°F per century (+0.10°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Oskaloosa's climate compare?
Oskaloosa is warmer than 111 of the other 131 places with their own NOAA record in Iowa, and wetter than 107. Across the 7,247 U.S. stations with normals, its annual mean of 50.1°F is warmer than 40%.
In the Köppen classification computed from these normals, Oskaloosa 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 Oskaloosa share this climate record?
7 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.
- New Sharon, IA1,249 people · 10 mi N
- University Park, IA476 people · 3 mi SE
- Beacon, IA434 people · 4 mi SW
- Rose Hill, IA156 people · 10 mi E
- Leighton, IA153 people · 7 mi W
- Barnes City, IA152 people · 16 mi NE
- Keomah Village, IA107 people · 6 mi SE
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 Oskaloosa's climate
What is the coldest month in Oskaloosa?
January, with a normal high of 31°F and a normal low of 12°F. The warmest is July (86°F by day, 65°F at night).
Does it snow in Oskaloosa?
Yes. NOAA publishes no 1991-2020 snowfall normal for Oskaloosa's NOAA station; the nearest record that keeps one, Ottumwa (18 miles away), records 24 inches of snow in a normal year.
What is the rainiest month in Oskaloosa?
June, with 5.18 in of precipitation in a normal year; the driest is December with 1.35 in.
What plant hardiness zone is Oskaloosa in?
The USDA's 2023 map puts Oskaloosa in zone 5b in ZIP code 52595, the nearest ZIP area.
How late can frost come in Oskaloosa?
In half of years the last 32°F night comes after April 21; in one year in ten it comes after May 4. Waiting until May 4 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Ottumwa, IA18 miles from this station, 50.7°F a year
- Albia, IA19 miles from this station, 50.0°F a year
- Sigourney, IA22 miles from this station, 48.9°F a year
- Knoxville, IA24 miles from this station, 49.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made