Romeoville, IL Climate: Temperature & Rain by Month
Explore NOAA NCEI's 1991–2020 climate normals → and a clearly labeled PlainClimate comfort calculation
30-year climate normals (1991-2020) from Romeoville's primary NOAA station, ROMEOVILLE WFO.
The climate verdict for Romeoville
Romeoville, Illinois has a mixed annual climate rather than one dominant extreme. Its NOAA normal shows an annual average of 51°F. Its climate comfort score of 63/100 (good) lands mid-pack nationally, exceeding 46% of station-mapped location scores.
- 51°F
- annual average temperature (NOAA normal)
- 63/100
- comfort score, above 46% of station-mapped location scores
- 41.1"
- annual precipitation · 33" snow
- 185 days
- frost-free days per growing season
Romeoville: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00117457 · Romeoville, IL 51°F mean · 41.1" precip
TEMP-COOL · RANK-MID · PHOTO-FINISH · PRCP-MID · SWING-WIDE · COMF-MID · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 51°F
- RANK-MID #3,019
- PHOTO-FINISH ≈ Valentine Nwr
- PRCP-MID 41.1"
- SWING-WIDE 51°F
- COMF-MID 63/100
- LOAD-HEAT 6,063 HDD
- STN-1 USC00117457
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Valentine Nwr, NE (+ 0 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every IL station list.
- Romeoville (this station) 51°F
- Cold Brady, NE 51°F
- Hot Valentine Nwr, NE 51°F
- Near Chicago Palwauk…, IL 51°F
- Near Fleming, CO 51°F
Climate Living Index · Romeoville
Romeoville: 55/100 · grade C
Romeoville publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Romeoville, not an official NOAA rating. Rankings still use Comfort Score 63/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Precipitation balance | 41.1 in · 6.1 from 35 in | 78/100 · B |
| Normal heat + freeze calendar | 130 calendar days | 59/100 · C |
| Frost-free season | 185 days/year | 54/100 · D |
| Annual temperature balance | 50.9°F · 16.6° from 67.5°F | 44/100 · D |
| Snowfall burden | 33.2 inches/year | 35/100 · F |
Romeoville · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Romeoville is a continental Köppen climate: Dfa
Coldest-month mean 23.9°F and warmest-month mean 74.6°F place this station in continental, no dry season, hot summer climates (Dfa). Class Dfa is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: continental, specifically continental, no dry season, hot summer.
- Köppen code
- Dfa
- Group
- Continental
- Warmest month
- 74.6°F
- Coldest month
- 23.9°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Romeoville sits across the climate record
Three NOAA fields for Romeoville's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 44th percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 61st percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Wider than 83%
- Warmest-to-coldest month gap for Romeoville is large versus 6,861 complete station-years.
How Romeoville compares across U.S. station-mapped locations
Romeoville's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
63 46th percentile score exceeds 46% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). This entry sits in this band.
- 70–80: 650 station-mapped locations (11%). Above this entry.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 32°F (0°C) | 16°F (-9°C) | 24°F (-5°C) | 2.2" | 10.6" | 28.2 | 0.0 |
| February | 36°F (2°C) | 20°F (-7°C) | 28°F (-2°C) | 2.0" | 8.7" | 24.8 | 0.0 |
| March | 49°F (9°C) | 30°F (-1°C) | 39°F (4°C) | 2.7" | 4.2" | 20.1 | 0.0 |
| April | 61°F (16°C) | 40°F (4°C) | 50°F (10°C) | 4.1" | 0.9" | 5.2 | 0.0 |
| May | 72°F (22°C) | 50°F (10°C) | 61°F (16°C) | 4.8" | 0.0" | 0.3 | 1.0 |
| June | 82°F (28°C) | 60°F (16°C) | 71°F (22°C) | 4.7" | 0.0" | 0.0 | 3.7 |
| July | 85°F (29°C) | 65°F (18°C) | 75°F (24°C) | 4.5" | 0.0" | 0.0 | 6.0 |
| August | 83°F (28°C) | 63°F (17°C) | 73°F (23°C) | 4.4" | 0.0" | 0.0 | 3.1 |
| September | 76°F (25°C) | 55°F (13°C) | 66°F (19°C) | 3.3" | 0.0" | 0.0 | 2.2 |
| October | 64°F (18°C) | 44°F (6°C) | 54°F (12°C) | 3.7" | 0.1" | 3.3 | 0.0 |
| November | 49°F (9°C) | 32°F (0°C) | 40°F (5°C) | 2.7" | 1.2" | 14.8 | 0.0 |
| December | 37°F (3°C) | 22°F (-6°C) | 29°F (-1°C) | 2.1" | 7.5" | 26.5 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 85°F around July 13, short of 90°F on every date, while 130 dates carry a normal low at or below freezing, the coldest 15°F near January 22.
The freezing stretch
The normal low stays at or below 32°F into March 23, then returns to freezing around November 15, covering 130 dates in all.
Derived from the normal daily minimum. This is a different measure from the 50%-probability frost dates shown elsewhere on this page, which come from NOAA’s frost product.
Where the wet dates fall
The likeliest wet date is May 10, when 44% of years recorded at least a hundredth of an inch. The driest is September 14 at 29%. Summed across the calendar, that is about 127 wet dates a year.
The widest day
May 6 carries the biggest normal gap between afternoon and dawn, 22°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Romeoville.
Where Romeoville Stands Nationally
Days and nights track unusually close together; the widest normal swing, about 22°F, is narrower than most stations record.
Romeoville earns one nationally notable standing (outer quintile) against 6,860 NOAA 1991–2020 normals stations, middle-of-the-pack metrics stay silent here.
Monthly Precipitation
Average monthly rainfall and snowfall
Snow: 10.6"
10.4 days with precipitation
Snow: 8.7"
9.6 days with precipitation
Snow: 4.2"
11.2 days with precipitation
Snow: 0.9"
12.2 days with precipitation
13.6 days with precipitation
11.7 days with precipitation
9.9 days with precipitation
9.8 days with precipitation
8.4 days with precipitation
Snow: 0.1"
10.6 days with precipitation
Snow: 1.2"
9.4 days with precipitation
Snow: 7.5"
10.5 days with precipitation
Romeoville spreads its precipitation across the year
Neither half of the year dominates here: June through August take 33% of the annual total and December through February 15%, with neither reaching the 35% that would mark a distinct wet season. Romeoville has no dry season to plan around, though it does carry a wide 50.7°F gap between its warmest and coldest month.
The gap between the wettest and driest month still matters: May averages 4.8" and February 2.0". The three wettest months together take 34% of the year, against the 25% a perfectly flat distribution would give them.
Shares are computed from this station's own 1991-2020 monthly precipitation normals. "Spread across the year" means neither the June-August nor the December-February share reaches 35%; it describes an average year, not the variability of any single one.
How Romeoville's precipitation splits across the calendar
About 127 days a year record measurable precipitation here, carrying 41.1" between them, or roughly 0.32 inches on a typical wet day. That sits in the middle band: neither the many-light-days pattern of the Pacific Northwest and the Great Lakes, nor the few-heavy-events pattern of the Gulf and the desert Southwest.
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year and say nothing about the heaviest single storm on record.
Winter brings real snow to Romeoville
Romeoville averages 33.2 inches of snowfall a year, with January the snowiest month on the normals, spread across roughly 26 days that record measurable snow. That is depth accumulating on the ground, which is why it can exceed the annual precipitation figure: precipitation counts the liquid the snow melts down to, and fresh snow is mostly air.
- Annual snowfall: 33.2 inches of depth.
- Days recording measurable snow: about 26 a year.
- At a rough ten-to-one melt ratio, snow accounts for on the order of 8% of the year's precipitation.
NOAA 1991-2020 normals. The ten-to-one ratio is a convention, not a measurement: real ratios vary with temperature, so treat the share as an order of magnitude rather than an exact split.
Frost Dates & Growing Season
First Fall Freeze
October 22
50% probability date
Last Spring Freeze
April 20
50% probability date
Growing Season
185 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
6,063
Higher = more heating needed
Cooling Degree Days
947
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Nationwide similar cities
Other rankable U.S. places outside IL closest to Romeoville on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (51°F here).
- Battle Ground, WA 51°F · 0.0°F off
- Belington, WV 51°F · 0.0°F off
- Blaine, WA 51°F · 0.0°F off
- Bland, VA 51°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (41.1" here), excluding temperature-peer places.
- Bloomingdale, MI 41.1" · 0.0" off
- Young America, IN 41.1" · 0.0" off
- Canton, PA 41.2" · 0.0" off
- Fredonia, NY 41.1" · 0.0" off
Snow and freeze rhythm
When cold and snow define Romeoville
heating led · moderate · mid swing
Romeoville's energy balance leans toward cold weather: 6,063 annual heating degree days against 947 for cooling. Its 50.7°F seasonal range still makes the monthly rows more useful than the annual average alone.
Romeoville's frost-free season lasts about 185 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
-
1. Romeoville coldest normal
January
Averaging 24°F (-5°C), this month sits below freezing for the month as a whole, not merely overnight.
-
2. Romeoville typical freeze period
January through December
The station reports average freezing days from January through December.
-
3. Romeoville snow peak
January
Romeoville averages 33.2 inches of snow a year, with January the snowiest month on the normals.
Questions about Romeoville's climate
How much snow does Romeoville get? ▼
How cold does Romeoville get in winter? ▼
How much energy does heating and cooling require in Romeoville? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Romeoville's primary station: ROMEOVILLE WFO (USC00117457). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The 2024 Census Gazetteer identifies the exact name-and-state match as an incorporated place (GEOID 1765442). Match rule for Romeoville: exact normalized name + state only, no fuzzy expansion, so nearby differently spelled facilities stay unmatched.
On this page every temperature, precipitation, and derived score for Romeoville comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.