In New Haven, July heat, January chill and rainfall all sit near the middle of U.S. towns
Midwinter brings lows of about 25°. It is a wet place: more rain and snow fall here than on 69% of U.S. towns. Warming shows here too: 0.7° more than in 1901–2000, led by February. Garden planting can start around April 15; autumn frost returns near October 19.
A year in New Haven at a glance
Each month’s typical high and low, and what it brings.
What stands out about New Haven’s climate
Compared with towns across the U.S., with New Haven’s place in Illinois beside it.
What a year in New Haven 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 15 and the first by October 19. Frost and day counts come from NOAA’s station at Carmi 3, IL, 12 miles from the town’s center, at about the same height.
The 2023 USDA map puts New Haven’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 1°. 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 8 inches of snow a winter
Snow, measured at Jt Myers Locks & Dam, IN, falls mostly in December. Precipitation (rain plus melted snow) adds up to 47 inches a year; April is the wettest month and February the driest. Rain or snow falls on about 107 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in New Haven
80% of the work is heating. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Carmi 3, IL.
Living with New Haven’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
183 frost-free days in zone 7a. The last frost comes by Apr 15 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 19.
Months with highs of 62–84° and lows of 40° or more: April, May, September and October.
Parks & trails →Of the yearly building losses FEMA expects in New Haven from natural hazards, river flooding is the largest share (41%); heat waves, cold waves, winter storms and ice storms together are 12%. Normals are averages; the hazards page covers the extremes.
Natural hazards →New Haven and its neighbors
Every town next door is within a degree of New Haven in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like New Haven’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 |
|---|---|---|---|---|
| New Haven, IL | 25° | 88° | 47" | 7.5" |
| Monett, MO | 24° | 89° | 47" | 6.7" |
| Penn Wynne, PA | 25° | 87° | 47" | 7.6" |
| Collinsville, VA | 27° | 88° | 46" | 9.4" |
| Harrison, AR | 26° | 89° | 47" | 9.5" |
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 New Haven averaged 0.7° warmer than the 1900s. The biggest change is in February (+1.8°).
A smaller shift than in 94% 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 New Haven compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with New Haven’s place among Illinois’.
New Haven weather by month
Highs, lows and precipitation from NOAA’s grid at New Haven’s center; snow, wet days and snow on the ground from Jt Myers Locks & Dam, IN. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 42° | 25° | 3.4" | 2.1" | 9 | 27° – 43° |
| February | 47° | 28° | 3.1" | 1.7" | 9 | 26° – 45° |
| March | 57° | 36° | 4.4" | 0.7" | 11 | 39° – 59° |
| April | 68° | 46° | 5.0" | 0.0" | 10 | 50° – 62° |
| May | 77° | 56° | 4.8" | 0.0" | 11 | 61° – 73° |
| June | 85° | 65° | 4.3" | 0.0" | 9 | 70° – 79° |
| July | 88° | 68° | 4.1" | 0.0" | 8 | 73° – 85° |
| August | 87° | 66° | 3.3" | 0.0" | 6 | 72° – 83° |
| September | 82° | 58° | 3.3" | 0.0" | 6 | 66° – 75° |
| October | 70° | 47° | 3.4" | 0.0" | 7 | 54° – 64° |
| November | 56° | 36° | 4.0" | 0.0" | 9 | 39° – 53° |
| December | 46° | 29° | 3.8" | 3.0" | 10 | 24° – 46° |
| Year | 67° | 47° | 46.9" | 7.5" | 107 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 24° to 46°. June is the most reliable, staying within 9°.
Where New Haven’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 New Haven’s center.
- Snow: Jt Myers Locks & Dam, IN.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Carmi 3, IL, 12 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 New Haven’s climate
What is the weather like in New Haven?
A typical July afternoon reaches 88°, a January night drops to 25°, and about 8 inches of snow falls in a normal winter. Milder January nights than 63% of U.S. towns; hotter July afternoons than 67% of U.S. towns.
How cold does it get in New Haven in winter?
January nights average 25°. About 103 nights a year reach 32° or below and 2 reach 0° or below. In the coldest January of the last 30 years the month averaged 27°.
How much snow does New Haven get?
About 7.5 inches in a normal winter at Jt Myers Locks & Dam, IN, most of it in December.
How hot does it get in New Haven?
July, with a typical high of 88° and a low of 68°. About 38 days a year reach 90° (Carmi 3, IL).
When is the first and last frost in New Haven?
In half of years the last spring frost (32°) comes by April 15 and the first fall frost by October 19, about 183 frost-free days, at Carmi 3, IL.
What growing zone is New Haven in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 1°.
What is the best time of year to visit New Haven?
By one simple rule (highs of 62–84° and lows of 40° or more), April, May, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is New Haven getting warmer?
Yes: 1991–2020 averaged 0.7° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 94% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in New Haven.
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.