Osage, Iowa climate: Normal weather by month, frost dates and records
Osage's normal year runs from 6°F January nights to 81°F July afternoons, with 37.6 inches of precipitation and 40 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.4°C, January lows of −14°C, July highs of 27°C, 955 mm of precipitation a year.
- NOAA stationOsage
- Station IDUSC00136305
- Location43.28°N 92.81°W
- Elevation1,170 ft (357 m)
- From the centerunder 1 mile
- Population3,559
On October 23, the normal high in Osage is 56°F and the normal low 35°F, and the chance of measurable rain or snow is 21%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Osage.
- Jan 23° 6°
- Feb 28° 10°
- Mar 41° 23°
- Apr 56° 35°
- May 68° 47°
- Jun 78° 58°
- Jul 81° 62°
- Aug 79° 59°
- Sep 73° 50°
- Oct 60° 38°
- Nov 43° 25°
- Dec 29° 14°
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 Osage each month?
July is the warmest month, with normal highs of 81°F; January the coldest, with normal lows of 6°F. The most precipitation falls in June (5.57 in), the least in January (1.17 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 23°F | 6°F | 14.7°F | 1.17 | 9.9 | 5 | <1 | 31 | 9 h 20 min |
| February | 28°F | 10°F | 19.1°F | 1.25 | 9.2 | 5 | <1 | 27 | 10 h 30 min |
| March | 41°F | 23°F | 31.9°F | 1.91 | 6.2 | 7 | <1 | 25 | 11 h 50 min |
| April | 56°F | 35°F | 45.5°F | 4.01 | 2.2 | 9 | <1 | 11 | 13 h 20 min |
| May | 68°F | 47°F | 57.8°F | 5.19 | 0.4 | 12 | 1 | 1 | 14 h 40 min |
| June | 78°F | 58°F | 68.0°F | 5.57 | 0.0 | 11 | 2 | <1 | 15 h 20 min |
| July | 81°F | 62°F | 71.6°F | 4.97 | 0.0 | 8 | 3 | <1 | 15 h 10 min |
| August | 79°F | 59°F | 69.1°F | 3.95 | 0.0 | 9 | 1 | <1 | 14 h |
| September | 73°F | 50°F | 61.7°F | 3.51 | 0.0 | 8 | 1 | <1 | 12 h 30 min |
| October | 60°F | 38°F | 48.6°F | 2.73 | 0.2 | 7 | <1 | 9 | 11 h 10 min |
| November | 43°F | 25°F | 33.9°F | 1.84 | 1.9 | 5 | <1 | 23 | 9 h 40 min |
| December | 29°F | 14°F | 21.4°F | 1.51 | 9.6 | 6 | <1 | 30 | 9 h |
| Year (annual) | 55°F | 36°F | 45.3°F | 37.61 | 39.6 | 92 | 8 | 156 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −5°C | −14°C | −9.6°C | 30 mm | 25 cm |
| February | −2°C | −12°C | −7.2°C | 32 mm | 23 cm |
| March | 5°C | −5°C | −0.1°C | 49 mm | 16 cm |
| April | 13°C | 2°C | 7.5°C | 102 mm | 6 cm |
| May | 20°C | 9°C | 14.3°C | 132 mm | 1 cm |
| June | 26°C | 15°C | 20.0°C | 141 mm | 0 cm |
| July | 27°C | 17°C | 22.0°C | 126 mm | 0 cm |
| August | 26°C | 15°C | 20.6°C | 100 mm | 0 cm |
| September | 23°C | 10°C | 16.5°C | 89 mm | 0 cm |
| October | 15°C | 3°C | 9.2°C | 69 mm | 1 cm |
| November | 6°C | −4°C | 1.1°C | 47 mm | 5 cm |
| December | −2°C | −10°C | −5.9°C | 38 mm | 24 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136305; 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 Osage?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. 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 USC00136305.
When is the last frost in Osage?
In Osage, the last spring frost (32°F) comes after April 30 in half of years and after May 12 in one year in ten; the first autumn frost comes before October 9 in half of years and before September 25 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 301 year in 10 after May 12; 9 in 10 after April 14
- First autumn frost, half of years before
- October 91 year in 10 before September 25; 9 in 10 before October 21
NOAA puts the median frost-free season at 163 days, and the season without a hard freeze (28°F) at 185 days.
A hard freeze (28°F) comes after April 17 in half of springs and before October 20 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Osage in zone 5a in ZIP code 50461, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Osage's NOAA station is in zone 5a: the coldest night of a typical year reaches −17°F (27 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 USC00136305; 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 Osage?
In a normal year in Osage, 8 days a year reach 90°F, 156 nights fall to 32°F or colder and 92 days bring measurable precipitation.
- Days at 90°F or more
- 8a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 156a normal year
- Days that stay below freezing
- 72high of 32°F or less
- Days with 0.01 inch of precipitation
- 92a normal year
- Days with 1 inch of snow or more
- 14a normal year
The highest temperature in this station's record (since 1894) is 107°F, on July 14, 1936; the lowest is −35°F, on January 12, 1912.
The wettest calendar year on that record is 2016, with 53.10 in; the snowiest season is 1950–51, with 77.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00136305; records: ACIS (NOAA Regional Climate Centers), station USC00136305. Records use complete months only; a month missing more than three days is left out.
How sunny is Osage?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Osage, 3.9 kWh per square metre a day. July is the sunniest month (81%) and December the cloudiest (63%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 69% | 1.8 |
| February | 75% | 3.0 |
| March | 69% | 3.7 |
| April | 68% | 4.7 |
| May | 70% | 5.5 |
| June | 75% | 6.1 |
| July | 81% | 6.3 |
| August | 79% | 5.4 |
| September | 77% | 4.3 |
| October | 69% | 2.8 |
| November | 68% | 1.9 |
| December | 63% | 1.4 |
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 Osage need?
A normal year in Osage brings 7,745 heating degree days, 44% more than the median U.S. place (5,373), and 593 cooling degree days, 35% fewer 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 2,618 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,559 | 0 |
| February | 1,285 | 0 |
| March | 1,026 | 0 |
| April | 586 | 3 |
| May | 256 | 33 |
| June | 45 | 136 |
| July | 9 | 212 |
| August | 23 | 148 |
| September | 156 | 55 |
| October | 514 | 6 |
| November | 935 | 0 |
| December | 1,352 | 0 |
| Year (annual) | 7,745 | 593 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136305. 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 Osage been warmer than normal lately?
2025 averaged 46.0°F, 0.7°F above the 1991-2020 normal of 45.3°F. 3 of the 3 complete years since 2023 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2023 | 47.3°F | +2.0°F | 31.03 | 28.0 |
| 2024 | 48.0°F | +2.7°F | 40.58 | – |
| 2025 | 46.0°F | +0.7°F | 41.57 | – |
Over 91 complete years from 1900 to 2025, the station's annual mean temperature rose at a fitted 2.1°F per century (+0.12°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00136305; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Osage's climate compare?
Osage is warmer than 9 of the other 131 places with their own NOAA record in Iowa, and wetter than 83. Across the 7,247 U.S. stations with normals, its annual mean of 45.3°F is warmer than 21%.
In the Köppen classification computed from these normals, Osage is Dfb: continental, no dry season, warm 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 Osage share this climate record?
10 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.
- Nora Springs, IA1,330 people · 14 mi SW
- St. Ansgar, IA1,172 people · 9 mi NW
- Le Roy, MN970 people · 22 mi NE
- Riceville, IA807 people · 14 mi NE
- Adams, MN700 people · 20 mi N
- Rudd, IA339 people · 12 mi SW
- Mitchell, IA118 people · 4 mi NW
- Orchard, IA64 people · 4 mi SE
- New Haven, IA58 people · 8 mi E
- Little Cedar, IA35 people · 8 mi NE
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 Osage's climate
What is the coldest month in Osage?
January, with a normal high of 23°F and a normal low of 6°F. The warmest is July (81°F by day, 62°F at night).
Does it snow in Osage?
Yes: 40 inches in a normal year, falling on 19 days with 0.1 inch or more, the most in January (9.9 inches).
What is the rainiest month in Osage?
June, with 5.57 in of precipitation in a normal year; the driest is January with 1.17 in.
What plant hardiness zone is Osage in?
The USDA's 2023 map puts Osage in zone 5a in ZIP code 50461, the nearest ZIP area. By the same method at Osage's NOAA station, the coldest night of a typical year reaches −17°F (27 years, 1991-2020): zone 5a.
How late can frost come in Osage?
In half of years the last 32°F night comes after April 30; in one year in ten it comes after May 12. Waiting until May 12 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Charles City, IA17 miles from this station, 46.5°F a year
- Northwood, IA24 miles from this station, 43.0°F a year
- Austin, MN27 miles from this station, 44.6°F a year
- Mason City, IA27 miles from this station, 45.6°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made