Photo: Jim Roberts · CC BY-SA 4.0Winter nights in Dexter are colder than in 91% of U.S. towns
July afternoons average 85°. May is the wettest month here, with about 6.1 times the rain of January. It is a dry place: less rain and snow fall here than on 77% of U.S. towns. The outdoor season runs from May to June and August to October, with highs of 64–83°.
A year in Dexter at a glance
Each month’s typical high and low, and what it brings.
What stands out about Dexter’s climate
Compared with towns across the U.S., with Dexter’s place in Iowa beside it.
What a year in Dexter feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 153 frost-free days a year
In half of years the last 32° night comes by May 2 and the first by October 3. Frost and day counts come from NOAA’s station at Guthrie Ctr, IA, 18 miles from the town’s center, at about the same height.
The 2023 USDA map puts Dexter’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −14°. 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 26 inches of snow a winter
Snow, measured at Greenfield, IA, is heaviest from January through February, about 7 inches a month. Precipitation (rain plus melted snow) adds up to 35 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 Dexter
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 Guthrie Ctr, IA.
Living with Dexter’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
153 frost-free days in zone 5b. The last frost comes by May 2 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, September and October. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Dexter from natural hazards, river flooding is the largest share (42%); heat waves, cold waves, winter storms and ice storms together are 14%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Dexter and similar climates
TownRatings has no climate map of the towns around Dexter yet.
Climates most like Dexter’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 |
|---|---|---|---|---|
| Dexter, IA | 12° | 85° | 35" | 26" |
| Colona, IL | 15° | 85° | 37" | 28" |
| Prairie du Chien, WI | 10° | 83° | 37" | 34" |
| Tecumseh, MI | 17° | 84° | 34" | 26" |
| Wauseon, OH | 18° | 84° | 35" | 27" |
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 Dexter averaged 0.5° warmer than the 1900s. The biggest change is in December (+2.2°).
A smaller shift than in 98% 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 Dexter compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Dexter’s place among Iowa’s.
Dexter weather by month
Highs, lows and precipitation from NOAA’s grid at Dexter’s center; snow, wet days and snow on the ground from Greenfield, IA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 30° | 12° | 0.8" | 6.8" | 6 | 17 | 13° – 34° |
| February | 35° | 16° | 1.1" | 7.3" | 7 | 16 | 16° – 36° |
| March | 48° | 27° | 2.0" | 3.0" | 8 | 6 | 30° – 53° |
| April | 62° | 38° | 3.7" | 0.8" | 11 | 1 | 41° – 56° |
| May | 72° | 50° | 5.1" | 0.1" | 13 | 0 | 55° – 68° |
| June | 81° | 60° | 5.0" | 0.0" | 11 | 0 | 67° – 75° |
| July | 85° | 64° | 4.1" | 0.0" | 9 | 0 | 69° – 81° |
| August | 83° | 61° | 4.1" | 0.0" | 9 | 0 | 66° – 77° |
| September | 76° | 52° | 3.5" | 0.0" | 8 | 0 | 58° – 69° |
| October | 64° | 40° | 2.7" | 0.4" | 9 | 0 | 45° – 57° |
| November | 48° | 28° | 1.7" | 1.7" | 6 | 2 | 29° – 49° |
| December | 35° | 18° | 1.3" | 5.4" | 7 | 11 | 11° – 34° |
| Year | 60° | 39° | 35.0" | 25.5" | 103 | 52 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 11° to 34°. June is the most reliable, staying within 8°.
Where Dexter’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 Dexter’s center.
- Snow: Greenfield, IA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Guthrie Ctr, IA, 18 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 Dexter’s climate
What is the weather like in Dexter?
A typical July afternoon reaches 85°, a January night drops to 12°, and about 26 inches of snow falls in a normal winter. Colder January nights than 91% of U.S. towns; cooler July afternoons than 52% of U.S. towns.
How cold does it get in Dexter in winter?
January nights average 12°. About 156 nights a year reach 32° or below and 18 reach 0° or below. In the coldest January of the last 30 years the month averaged 13°.
How much snow does Dexter get?
About 26 inches in a normal winter at Greenfield, IA, heaviest from January through February, about 7 inches a month, with snow on the ground about 52 days a year.
How hot does it get in Dexter?
July, with a typical high of 85° and a low of 64°. About 21 days a year reach 90° (Guthrie Ctr, IA).
When is the first and last frost in Dexter?
In half of years the last spring frost (32°) comes by May 2 and the first fall frost by October 3, about 153 frost-free days, at Guthrie Ctr, IA.
What growing zone is Dexter in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −14°.
What is the best time of year to visit Dexter?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Dexter getting warmer?
Yes: 1991–2020 averaged 0.5° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 98% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Dexter.
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.