Winter nights in Union are colder than in 94% of U.S. towns
The warmest part of a July day comes in at 84° on average. June is the wettest month, January the driest. Its yearly precipitation falls short of 74% of U.S. towns. Warm coats and heating bills mark the months from November to April, when means dip under 50°.
A year in Union at a glance
Each month’s typical high and low, and what it brings.
What stands out about Union’s climate
Compared with towns across the U.S., with Union’s place in Iowa beside it.
What a year in Union feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 165 frost-free days a year
In half of years the last 32° night comes by April 27 and the first by October 10. Frost and day counts come from NOAA’s station at Eldora, IA, 9 miles from the town’s center, 150 ft higher.
The 2023 USDA map puts Union’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 33 inches of snow a winter
Snow, measured at Eldora, IA, falls mostly in January, February and December. Precipitation (rain plus melted snow) adds up to 36 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 112 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Union
91% 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 Eldora, IA.
Living with Union’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
165 frost-free days in zone 5a. The last frost comes by Apr 27 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 10.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September.
Parks & trails →Of the yearly building losses FEMA expects in Union from natural hazards, hail is the largest share (32%); heat waves, cold waves, winter storms and ice storms together are 9%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Union and similar climates
TownRatings has no climate map of the towns around Union yet.
Climates most like Union’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 |
|---|---|---|---|---|
| Union, IA | 10° | 84° | 36" | 33" |
| Edgerton, WI | 12° | 83° | 37" | 36" |
| Freeport, IL | 12° | 83° | 38" | 35" |
| Lake City, MN | 6° | 83° | 35" | 34" |
| Blair, NE | 14° | 85° | 32" | 32" |
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 Union averaged 0.7° warmer than the 1900s. The biggest change is in December (+2.3°).
A smaller shift than in 93% 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 Union compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Union’s place among Iowa’s.
Union weather by month
Highs, lows and precipitation from NOAA’s grid at Union’s center; snow, wet days and snow on the ground from Eldora, IA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 27° | 10° | 0.9" | 8.1" | 7 | 22 | 8° – 31° |
| February | 32° | 14° | 1.1" | 8.8" | 7 | 20 | 12° – 34° |
| March | 46° | 26° | 1.9" | 4.0" | 8 | 9 | 27° – 51° |
| April | 60° | 37° | 3.8" | 1.4" | 11 | 1 | 39° – 55° |
| May | 71° | 49° | 4.9" | 0.4" | 14 | 0 | 54° – 68° |
| June | 81° | 59° | 5.7" | 0.0" | 13 | 0 | 67° – 74° |
| July | 84° | 63° | 4.2" | 0.0" | 10 | 0 | 68° – 79° |
| August | 82° | 60° | 4.2" | 0.0" | 10 | 0 | 65° – 76° |
| September | 76° | 51° | 3.4" | 0.0" | 9 | 0 | 57° – 69° |
| October | 62° | 39° | 2.7" | 0.3" | 9 | 0 | 45° – 56° |
| November | 46° | 27° | 1.9" | 1.8" | 7 | 3 | 28° – 48° |
| December | 33° | 16° | 1.4" | 8.4" | 8 | 15 | 9° – 34° |
| Year | 58° | 38° | 35.9" | 33.2" | 112 | 69 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 9° to 34°. June is the most reliable, staying within 7°.
Where Union’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 Union’s center.
- Snow: Eldora, IA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Eldora, IA, 9 miles from the town’s center, 150 ft higher; 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 Union’s climate
What is the weather like in Union?
A typical July afternoon reaches 84°, a January night drops to 10°, and about 33 inches of snow falls in a normal winter. Colder January nights than 94% of U.S. towns; cooler July afternoons than 63% of U.S. towns.
How cold does it get in Union in winter?
January nights average 10°. About 153 nights a year reach 32° or below and 21 reach 0° or below. In the coldest January of the last 30 years the month averaged 8°.
How much snow does Union get?
About 33 inches in a normal winter at Eldora, IA, most of it in January, February and December, with snow on the ground about 69 days a year.
How hot does it get in Union?
July, with a typical high of 84° and a low of 63°. About 16 days a year reach 90° (Eldora, IA).
When is the first and last frost in Union?
In half of years the last spring frost (32°) comes by April 27 and the first fall frost by October 10, about 165 frost-free days, at Eldora, IA.
What growing zone is Union 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 Union?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Union getting warmer?
Yes: 1991–2020 averaged 0.7° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 93% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Union.
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.