Fitzpatrick House · Photo: Teemu08 at en.wikipedia · CC BY-SA 3.0Romeoville has colder winter nights than 79% of U.S. towns
Sunny July days climb to about 84°. A year here swings 68° from midwinter lows to midsummer highs. Precipitation is light here, less than falls on 64% of U.S. towns. Radiators earn their keep from November to April, the months that average under 50°.
A year in Romeoville at a glance
Each month’s typical high and low, and what it brings.
What stands out about Romeoville’s climate
Compared with towns across the U.S., with Romeoville’s place in Illinois beside it.
What a year in Romeoville feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 184 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 Romeoville Wfo, IL, 1.8 miles from the town’s center, at about the same height.
The 2023 USDA map puts Romeoville’s center in zone 6a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −10°. 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 Romeoville Wfo, IL, falls mostly in January. Precipitation (rain plus melted snow) adds up to 39 inches a year; May is the wettest month and February the driest. Rain or snow falls on about 127 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Romeoville
86% 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 Romeoville Wfo, IL.
Living with Romeoville’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
184 frost-free days in zone 6a. 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. 18 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Romeoville from natural hazards, river flooding is the largest share (41%); heat waves, cold waves, winter storms and ice storms together are 28%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Romeoville and its neighbors
Every town next door is within a degree of Romeoville in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Romeoville’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 |
|---|---|---|---|---|
| Romeoville, IL | 16° | 84° | 39" | 33" |
| Fort Wayne, IN | 18° | 84° | 39" | 34" |
| Sayre, PA | 17° | 84° | 37" | 35" |
| Claverack, NY | 16° | 84° | 42" | 31" |
| Bryan, OH | 18° | 84° | 37" | 29" |
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 Romeoville averaged 1.3° warmer than the 1900s. The biggest change is in December (+2.5°).
A smaller shift than in 57% 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 Romeoville compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Romeoville’s place among Illinois’.
Romeoville weather by month
Highs, lows and precipitation from NOAA’s grid at Romeoville’s center; snow, wet days and snow on the ground from Romeoville Wfo, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 31° | 16° | 2.1" | 10.6" | 10 | 15 | 14° – 36° |
| February | 36° | 20° | 1.8" | 8.7" | 10 | 11 | 15° – 39° |
| March | 48° | 29° | 2.4" | 4.2" | 11 | 3 | 30° – 53° |
| April | 61° | 39° | 3.9" | 0.9" | 12 | 0 | 41° – 56° |
| May | 72° | 50° | 4.5" | 0.0" | 14 | 0 | 55° – 67° |
| June | 81° | 59° | 4.5" | 0.0" | 12 | 0 | 66° – 75° |
| July | 84° | 64° | 4.0" | 0.0" | 10 | 0 | 69° – 81° |
| August | 83° | 62° | 4.1" | 0.0" | 10 | 0 | 67° – 78° |
| September | 76° | 55° | 3.3" | 0.0" | 8 | 0 | 60° – 70° |
| October | 64° | 43° | 3.4" | 0.1" | 11 | 0 | 49° – 60° |
| November | 49° | 32° | 2.6" | 1.2" | 9 | 1 | 32° – 49° |
| December | 36° | 22° | 2.2" | 7.5" | 11 | 9 | 16° – 39° |
| Year | 60° | 41° | 38.9" | 33.2" | 127 | 39 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 15° to 39°. June is the most reliable, staying within 9°.
Where Romeoville’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 Romeoville’s center.
- Snow: Romeoville Wfo, IL (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Romeoville Wfo, IL, 1.8 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 Romeoville’s climate
What is the weather like in Romeoville?
A typical July afternoon reaches 84°, a January night drops to 16°, and about 33 inches of snow falls in a normal winter. Colder January nights than 79% of U.S. towns; cooler July afternoons than 57% of U.S. towns.
How cold does it get in Romeoville in winter?
January nights average 16°. About 123 nights a year reach 32° or below and 8 reach 0° or below. In the coldest January of the last 30 years the month averaged 14°.
How much snow does Romeoville get?
About 33 inches in a normal winter at Romeoville Wfo, IL, most of it in January, with snow on the ground about 39 days a year.
How hot does it get in Romeoville?
July, with a typical high of 84° and a low of 64°. About 16 days a year reach 90° (Romeoville Wfo, IL).
When is the first and last frost in Romeoville?
In half of years the last spring frost (32°) comes by April 20 and the first fall frost by October 22, about 184 frost-free days, at Romeoville Wfo, IL.
What growing zone is Romeoville in?
Zone 6a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −10°.
What is the best time of year to visit Romeoville?
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 Romeoville getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 57% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Romeoville.
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.