Onawa, Iowa climate: Normal weather by month, frost dates and records
Onawa's normal year runs from 9°F January nights to 86°F July afternoons, with 29.9 inches of precipitation and 31 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.2°C, January lows of −13°C, July highs of 30°C, 758 mm of precipitation a year.
- NOAA stationOnawa (3 mi NW)
- Station IDUSC00136243
- Location42.07°N 96.13°W
- Elevation1,060 ft (323 m)
- From the center3 miles
- Population2,795
On October 23, the normal high in Onawa is 62°F and the normal low 34°F, and the chance of measurable rain or snow is 16%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Onawa.
- Jan 30° 9°
- Feb 36° 13°
- Mar 50° 24°
- Apr 63° 35°
- May 74° 48°
- Jun 83° 59°
- Jul 86° 63°
- Aug 84° 59°
- Sep 78° 50°
- Oct 65° 37°
- Nov 49° 24°
- Dec 34° 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 Onawa each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 9°F. The most precipitation falls in May (4.58 in), the least in January (0.54 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 30°F | 9°F | 19.4°F | 0.54 | 7.9 | 5 | <1 | 31 | 9 h 30 min |
| February | 36°F | 13°F | 24.0°F | 0.78 | 6.6 | 4 | <1 | 26 | 10 h 30 min |
| March | 50°F | 24°F | 36.8°F | 1.57 | 4.5 | 6 | <1 | 23 | 11 h 50 min |
| April | 63°F | 35°F | 48.7°F | 3.28 | 1.8 | 8 | <1 | 9 | 13 h 20 min |
| May | 74°F | 48°F | 60.7°F | 4.58 | 0.0 | 9 | 2 | 1 | 14 h 30 min |
| June | 83°F | 59°F | 71.0°F | 4.18 | 0.0 | 9 | 6 | <1 | 15 h 10 min |
| July | 86°F | 63°F | 74.3°F | 3.39 | 0.0 | 8 | 9 | <1 | 15 h |
| August | 84°F | 59°F | 71.5°F | 4.07 | 0.0 | 7 | 6 | <1 | 14 h |
| September | 78°F | 50°F | 64.2°F | 2.97 | 0.0 | 6 | 3 | 1 | 12 h 30 min |
| October | 65°F | 37°F | 51.3°F | 2.31 | 0.3 | 5 | 1 | 9 | 11 h 10 min |
| November | 49°F | 24°F | 36.1°F | 1.50 | 2.8 | 5 | <1 | 23 | 9 h 50 min |
| December | 34°F | 14°F | 24.0°F | 0.69 | 7.1 | 4 | <1 | 30 | 9 h 10 min |
| Year (annual) | 61°F | 36°F | 48.5°F | 29.86 | 31.0 | 75 | 27 | 151 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −13°C | −7.0°C | 14 mm | 20 cm |
| February | 2°C | −11°C | −4.4°C | 20 mm | 17 cm |
| March | 10°C | −5°C | 2.7°C | 40 mm | 11 cm |
| April | 17°C | 2°C | 9.3°C | 83 mm | 5 cm |
| May | 23°C | 9°C | 15.9°C | 116 mm | 0 cm |
| June | 28°C | 15°C | 21.7°C | 106 mm | 0 cm |
| July | 30°C | 17°C | 23.5°C | 86 mm | 0 cm |
| August | 29°C | 15°C | 21.9°C | 103 mm | 0 cm |
| September | 26°C | 10°C | 17.9°C | 75 mm | 0 cm |
| October | 19°C | 3°C | 10.7°C | 59 mm | 1 cm |
| November | 9°C | −5°C | 2.3°C | 38 mm | 7 cm |
| December | 1°C | −10°C | −4.4°C | 18 mm | 18 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136243; 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 Onawa?
Normal highs sit between 65°F and 85°F in May, June, August, September and October. Of those, October has the fewest days with rain (5).
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 USC00136243.
When is the last frost in Onawa?
In Onawa, the last spring frost (32°F) comes after May 1 in half of years and after May 13 in one year in ten; the first autumn frost comes before October 3 in half of years and before September 21 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
- May 11 year in 10 after May 13; 9 in 10 after April 19
- First autumn frost, half of years before
- October 31 year in 10 before September 21; 9 in 10 before October 18
NOAA puts the median frost-free season at 154 days, and the season without a hard freeze (28°F) at 172 days.
A hard freeze (28°F) comes after April 22 in half of springs and before October 13 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Onawa in zone 5a in ZIP code 51040, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Onawa's NOAA station is in zone 5a: the coldest night of a typical year reaches −17°F (19 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 USC00136243; 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 Onawa?
In a normal year in Onawa, 27 days a year reach 90°F (1 of them 100°F or more), 151 nights fall to 32°F or colder and 75 days bring measurable precipitation.
- Days at 90°F or more
- 27a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 151a normal year
- Days that stay below freezing
- 49high of 32°F or less
- Days with 0.01 inch of precipitation
- 75a normal year
- Days with 1 inch of snow or more
- 10a normal year
The highest temperature in this station's record (since 1899) is 110°F, on July 26, 1936; the lowest is −32°F, on January 12, 1912.
The wettest calendar year on that record is 1903, with 50.53 in; the snowiest season is 1911–12, with 85.4 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00136243; records: ACIS (NOAA Regional Climate Centers), station USC00136243. Records use complete months only; a month missing more than three days is left out.
How sunny is Onawa?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Onawa, 4.2 kWh per square metre a day. July is the sunniest month (84%) and December the cloudiest (69%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 72% | 2.0 |
| February | 77% | 3.1 |
| March | 70% | 3.8 |
| April | 71% | 5.0 |
| May | 72% | 5.8 |
| June | 79% | 6.5 |
| July | 84% | 6.6 |
| August | 81% | 5.6 |
| September | 80% | 4.5 |
| October | 75% | 3.1 |
| November | 75% | 2.2 |
| December | 69% | 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 Onawa need?
A normal year in Onawa brings 6,845 heating degree days, 27% more than the median U.S. place (5,373), and 876 cooling degree days, 3% 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 3,119 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,415 | 0 |
| February | 1,146 | 0 |
| March | 873 | 0 |
| April | 495 | 6 |
| May | 190 | 57 |
| June | 21 | 203 |
| July | 4 | 292 |
| August | 13 | 216 |
| September | 115 | 90 |
| October | 435 | 12 |
| November | 866 | 0 |
| December | 1,272 | 0 |
| Year (annual) | 6,845 | 876 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00136243. 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 Onawa's climate compare?
Onawa is warmer than 76 of the other 131 places with their own NOAA record in Iowa, and wetter than 7. Across the 7,247 U.S. stations with normals, its annual mean of 48.5°F is warmer than 34%.
In the Köppen classification computed from these normals, Onawa 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 Onawa share this climate record?
4 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.
- Lyons, NE812 people · 20 mi SW
- Macy, NE795 people · 13 mi W
- Whiting, IA725 people · 4 mi N
- Decatur, NE411 people · 8 mi SW
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 Onawa's climate
What is the coldest month in Onawa?
January, with a normal high of 30°F and a normal low of 9°F. The warmest is July (86°F by day, 63°F at night).
Does it snow in Onawa?
Yes: 31 inches in a normal year, falling on 16 days with 0.1 inch or more, the most in January (7.9 inches).
What is the rainiest month in Onawa?
May, with 4.58 in of precipitation in a normal year; the driest is January with 0.54 in.
What plant hardiness zone is Onawa in?
The USDA's 2023 map puts Onawa in zone 5a in ZIP code 51040, the nearest ZIP area. By the same method at Onawa's NOAA station, the coldest night of a typical year reaches −17°F (19 years, 1991-2020): zone 5a.
How late can frost come in Onawa?
In half of years the last 32°F night comes after May 1; in one year in ten it comes after May 13. Waiting until May 13 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iowa climateThe statewide normals and every place in the state
- Castana, IA15 miles from this station, 48.2°F a year
- Little Sioux, IA17 miles from this station, 48.1°F a year
- Mapleton, IA19 miles from this station, 47.2°F a year
- Walthill, NE19 miles from this station, 49.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made