Photo: Jared Winkler · CC BY-SA 4.0Onawa’s winters are colder and snowier than most of the U.S.
A typical July afternoon reaches 86°, a January night drops to 11°, and about 24 inches of snow falls in a normal winter.
A year in Onawa at a glance
Each month’s typical high and low, and what it brings.
What stands out about Onawa’s climate
Compared with towns across the U.S., with Onawa’s place in Iowa beside it.
What a year in Onawa feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 154 frost-free days a year
In half of years the last 32° night comes by May 1 and the first by October 3. Frost and day counts come from NOAA’s station at Onawa 3nw, IA, 3 miles from the town’s center, at about the same height.
The 2023 USDA map puts Onawa’s center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −16°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 24 inches of snow a winter
Snow, measured at Kennebec, IA, falls mostly in December. Precipitation (rain plus melted snow) adds up to 30 inches a year; May is the wettest month and January the driest. Rain or snow falls on about 80 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Onawa
89% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Onawa 3nw, IA.
Living with Onawa’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
154 frost-free days in zone 5a. The last frost comes by May 1 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 3.
Months with highs of 62–84° and lows of 40° or more: May, June, August and September. 0.9 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Onawa from natural hazards, tornadoes are the largest share (38%); heat waves, cold waves, winter storms and ice storms together are 16%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Onawa and similar climates
TownRatings has no climate map of the towns around Onawa yet.
Climates most like Onawa’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Onawa, IA | 11° | 86° | 30" | 24" |
| Hastings, NE | 15° | 87° | 27" | 29" |
| Ottawa, IL | 16° | 85° | 37" | 24" |
| Tecumseh, MI | 17° | 84° | 34" | 26" |
| Mitchell, SD | 8° | 86° | 25" | 41" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Onawa averaged 1.1° warmer than the 1900s. The biggest change is in March (+2.4°).
A smaller shift than in 71% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Onawa compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Onawa’s place among Iowa’s.
Onawa weather by month
Highs, lows and precipitation from NOAA’s grid at Onawa’s center; snow, wet days and snow on the ground from Kennebec, IA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 30° | 11° | 0.7" | 5.7" | 4 | 15 | 13° – 34° |
| February | 35° | 16° | 0.8" | 4.9" | 5 | 17 | 15° – 35° |
| March | 49° | 27° | 1.7" | 3.4" | 6 | 3 | 31° – 53° |
| April | 62° | 37° | 3.2" | 1.6" | 9 | 0 | 41° – 56° |
| May | 73° | 49° | 4.5" | 0.0" | 11 | 0 | 56° – 67° |
| June | 83° | 60° | 4.4" | 0.0" | 10 | 0 | 68° – 76° |
| July | 86° | 64° | 3.4" | 0.0" | 8 | 0 | 69° – 81° |
| August | 83° | 61° | 3.9" | 0.0" | 7 | 0 | 67° – 77° |
| September | 77° | 52° | 3.2" | 0.0" | 6 | 0 | 58° – 70° |
| October | 64° | 40° | 2.2" | 0.5" | 6 | 0 | 45° – 56° |
| November | 48° | 26° | 1.4" | 0.9" | 4 | 1 | 27° – 48° |
| December | 34° | 16° | 1.1" | 6.9" | 5 | 12 | 12° – 31° |
| Year | 60° | 38° | 30.3" | 23.9" | 80 | 48 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 31° to 53°. June is the most reliable, staying within 8°.
Where Onawa’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Onawa’s center.
- Snow: Kennebec, IA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Onawa 3nw, IA, 3 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Onawa’s climate
What is the weather like in Onawa?
A typical July afternoon reaches 86°, a January night drops to 11°, and about 24 inches of snow falls in a normal winter. Colder January nights than 92% of U.S. towns; hotter July afternoons than 55% of U.S. towns.
How cold does it get in Onawa in winter?
January nights average 11°. About 151 nights a year reach 32° or below and 16 reach 0° or below. In the coldest January of the last 30 years the month averaged 13°.
How much snow does Onawa get?
About 24 inches in a normal winter at Kennebec, IA, most of it in December, with snow on the ground about 48 days a year.
How hot does it get in Onawa?
July, with a typical high of 86° and a low of 64°. About 27 days a year reach 90° (Onawa 3nw, IA).
When is the first and last frost in Onawa?
In half of years the last spring frost (32°) comes by May 1 and the first fall frost by October 3, about 154 frost-free days, at Onawa 3nw, IA.
What growing zone is Onawa in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −16°.
What is the best time of year to visit Onawa?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Onawa getting warmer?
Yes: 1991–2020 averaged 1.1° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 71% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Onawa.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.