Photo: PopePompus · CC BY-SA 4.0Midwinter lows in Unionville sink below those of 85% of U.S. towns
In July the day’s top temperature is typically 85°. Its yearly precipitation falls short of 69% of U.S. towns. Compared with 1901–2000, the average now sits 0.5° higher. Plan time outside from April to June and August to October, when highs sit at 62–84°.
A year in Unionville at a glance
Each month’s typical high and low, and what it brings.
What stands out about Unionville’s climate
Compared with towns across the U.S., with Unionville’s place in Iowa beside it.
What a year in Unionville feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 187 frost-free days a year
In half of years the last 32° night comes by April 18 and the first by October 23. Frost and day counts come from NOAA’s station at Rathbun Dam, IA, 10 miles from the town’s center, at about the same height.
The 2023 USDA map puts Unionville’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −12°. 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 Bloomfield, IA, falls mostly in January. Precipitation (rain plus melted snow) adds up to 38 inches a year; May is the wettest month and January the driest. Rain or snow falls on about 103 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Unionville
87% 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 Rathbun Dam, IA.
Living with Unionville’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
187 frost-free days in zone 5b. The last frost comes by Apr 18 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 23.
Months with highs of 62–84° and lows of 40° or more: April, May, June, August, September and October. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Unionville from natural hazards, drought is the largest share (34%); heat waves, cold waves, winter storms and ice storms together are 14%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Unionville and similar climates
TownRatings has no climate map of the towns around Unionville yet.
Climates most like Unionville’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 |
|---|---|---|---|---|
| Unionville, IA | 15° | 85° | 38" | 24" |
| Ottawa, IL | 16° | 85° | 37" | 24" |
| Schererville, IN | 17° | 84° | 39" | 27" |
| Defiance, OH | 19° | 85° | 37" | 24" |
| Claverack, NY | 16° | 84° | 42" | 31" |
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 Unionville averaged 0.5° warmer than the 1900s. The biggest change is in December (+2.1°).
A smaller shift than in 97% 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 Unionville compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Unionville’s place among Iowa’s.
Unionville weather by month
Highs, lows and precipitation from NOAA’s grid at Unionville’s center; snow, wet days and snow on the ground from Bloomfield, IA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 32° | 15° | 1.2" | 7.4" | 7 | 17 | 16° – 35° |
| February | 37° | 19° | 1.5" | 5.5" | 7 | 12 | 16° – 39° |
| March | 50° | 29° | 2.2" | 3.2" | 8 | 4 | 32° – 54° |
| April | 62° | 40° | 3.9" | 1.5" | 10 | 0 | 43° – 58° |
| May | 72° | 51° | 5.2" | 0.0" | 13 | 0 | 56° – 69° |
| June | 81° | 61° | 5.2" | 0.0" | 11 | 0 | 68° – 75° |
| July | 85° | 65° | 4.1" | 0.0" | 8 | 0 | 69° – 82° |
| August | 84° | 62° | 4.2" | 0.0" | 9 | 0 | 67° – 78° |
| September | 76° | 54° | 3.8" | 0.0" | 8 | 0 | 59° – 70° |
| October | 64° | 42° | 2.9" | 0.0" | 8 | 0 | 47° – 58° |
| November | 49° | 31° | 2.1" | 1.5" | 7 | 2 | 32° – 50° |
| December | 37° | 20° | 1.6" | 5.1" | 7 | 8 | 14° – 38° |
| Year | 61° | 41° | 37.8" | 24.2" | 103 | 44 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 14° to 38°. June is the most reliable, staying within 7°.
Where Unionville’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 Unionville’s center.
- Snow: Bloomfield, IA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Rathbun Dam, IA, 10 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 Unionville’s climate
What is the weather like in Unionville?
A typical July afternoon reaches 85°, a January night drops to 15°, and about 24 inches of snow falls in a normal winter. Colder January nights than 85% of U.S. towns; hotter July afternoons than 51% of U.S. towns.
How cold does it get in Unionville in winter?
January nights average 15°. About 136 nights a year reach 32° or below and 13 reach 0° or below. In the coldest January of the last 30 years the month averaged 16°.
How much snow does Unionville get?
About 24 inches in a normal winter at Bloomfield, IA, most of it in January, with snow on the ground about 44 days a year.
How hot does it get in Unionville?
July, with a typical high of 85° and a low of 65°. About 19 days a year reach 90° (Rathbun Dam, IA).
When is the first and last frost in Unionville?
In half of years the last spring frost (32°) comes by April 18 and the first fall frost by October 23, about 187 frost-free days, at Rathbun Dam, IA.
What growing zone is Unionville in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −12°.
What is the best time of year to visit Unionville?
By one simple rule (highs of 62–84° and lows of 40° or more), April, May, June, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Unionville getting warmer?
Yes: 1991–2020 averaged 0.5° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 97% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Unionville.
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.