Dayton’s winters are colder and snowier than most of the U.S.
A typical July afternoon reaches 84°, a January night drops to 15°, and about 24 inches of snow falls in a normal winter.
A year in Dayton at a glance
Each month’s typical high and low, and what it brings.
What stands out about Dayton’s climate
Compared with towns across the U.S., with Dayton’s place in Illinois beside it.
What a year in Dayton feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 183 frost-free days a year
In half of years the last 32° night comes by April 20 and the first by October 22. Frost and day counts come from NOAA’s station at Ottawa 5sw, IL, 7 miles from the town’s center, at about the same height.
The 2023 USDA map puts Dayton’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −11°. 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 Ottawa 5sw, IL, falls mostly in January. Precipitation (rain plus melted snow) adds up to 37 inches a year; May is the wettest month and February 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 Dayton
88% 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 Ottawa 5sw, IL.
Living with Dayton’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
183 frost-free days in zone 5b. The last frost comes by Apr 20 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 22.
Months with highs of 62–84° and lows of 40° or more: May, June, August, September and October.
Parks & trails →Of the yearly building losses FEMA expects in Dayton from natural hazards, river flooding is the largest share (59%); heat waves, cold waves, winter storms and ice storms together are 19%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Dayton and its neighbors
Every town next door is within a degree of Dayton in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Dayton’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 |
|---|---|---|---|---|
| Dayton, IL | 15° | 84° | 37" | 24" |
| Fairfield, IA | 14° | 85° | 38" | 22" |
| Defiance, OH | 19° | 85° | 37" | 24" |
| Auburn, IN | 17° | 84° | 38" | 30" |
| Tecumseh, MI | 17° | 84° | 34" | 26" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Dayton averaged 1.3° warmer than the 1900s. The biggest change is in December (+2.5°).
A smaller shift than in 58% 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 Dayton compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Dayton’s place among Illinois’.
Dayton weather by month
Highs, lows and precipitation from NOAA’s grid at Dayton’s center; snow, wet days and snow on the ground from Ottawa 5sw, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 31° | 15° | 1.9" | 9.2" | 9 | 17 | 15° – 35° |
| February | 36° | 19° | 1.8" | 5.2" | 8 | 11 | 14° – 38° |
| March | 48° | 29° | 2.3" | 3.3" | 9 | 4 | 30° – 54° |
| April | 62° | 39° | 3.6" | 0.4" | 12 | 0 | 41° – 57° |
| May | 73° | 50° | 4.6" | 0.0" | 12 | 0 | 55° – 68° |
| June | 82° | 59° | 4.5" | 0.0" | 11 | 0 | 67° – 74° |
| July | 84° | 63° | 3.8" | 0.0" | 8 | 0 | 69° – 80° |
| August | 83° | 61° | 3.8" | 0.0" | 9 | 0 | 66° – 78° |
| September | 77° | 54° | 3.3" | 0.0" | 8 | 0 | 60° – 70° |
| October | 64° | 42° | 3.1" | 0.0" | 9 | 0 | 48° – 59° |
| November | 49° | 31° | 2.5" | 0.8" | 9 | 1 | 32° – 49° |
| December | 36° | 21° | 2.0" | 4.8" | 9 | 9 | 14° – 39° |
| Year | 60° | 40° | 37.1" | 23.7" | 112 | 43 |
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 39°. June is the most reliable, staying within 8°.
Where Dayton’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 Dayton’s center.
- Snow: Ottawa 5sw, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Ottawa 5sw, IL, 7 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 Dayton’s climate
What is the weather like in Dayton?
A typical July afternoon reaches 84°, a January night drops to 15°, and about 24 inches of snow falls in a normal winter. Colder January nights than 83% of U.S. towns; cooler July afternoons than 56% of U.S. towns.
How cold does it get in Dayton in winter?
January nights average 15°. About 129 nights a year reach 32° or below and 9 reach 0° or below. In the coldest January of the last 30 years the month averaged 15°.
How much snow does Dayton get?
About 24 inches in a normal winter at Ottawa 5sw, IL, most of it in January, with snow on the ground about 43 days a year.
How hot does it get in Dayton?
July, with a typical high of 84° and a low of 63°. About 17 days a year reach 90° (Ottawa 5sw, IL).
When is the first and last frost in Dayton?
In half of years the last spring frost (32°) comes by April 20 and the first fall frost by October 22, about 183 frost-free days, at Ottawa 5sw, IL.
What growing zone is Dayton in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −11°.
What is the best time of year to visit Dayton?
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 Dayton getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 58% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Dayton.
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.