West Chicago, Illinois climate: Normal weather by month, frost dates and records
West Chicago's normal year runs from 16°F January nights to 84°F July afternoons, with 33.2 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.8°C, January lows of −9°C, July highs of 29°C, 844 mm of precipitation a year.
- NOAA stationWest Chicago Dupage Airport
- Station IDUSW00094892
- Location41.91°N 88.25°W
- Elevation754 ft (230 m)
- From the center2 miles
- Population25,469
On October 14, the normal high in West Chicago is 63°F and the normal low 43°F, and the chance of measurable rain or snow is 34%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for West Chicago.
- Jan 31° 16°
- Feb 35° 19°
- Mar 47° 28°
- Apr 60° 38°
- May 71° 49°
- Jun 81° 59°
- Jul 84° 63°
- Aug 82° 62°
- Sep 76° 54°
- Oct 62° 42°
- Nov 48° 31°
- Dec 35° 21°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in West Chicago each month?
July is the warmest month, with normal highs of 84°F; January the coldest, with normal lows of 16°F. The most precipitation falls in May (4.34 in), the least in February (1.24 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 31°F | 16°F | 23.3°F | 1.27 | 8 | <1 | 29 | 9 h 30 min |
| February | 35°F | 19°F | 27.0°F | 1.24 | 7 | <1 | 26 | 10 h 30 min |
| March | 47°F | 28°F | 37.7°F | 1.97 | 9 | <1 | 21 | 11 h 50 min |
| April | 60°F | 38°F | 48.8°F | 3.44 | 12 | <1 | 8 | 13 h 20 min |
| May | 71°F | 49°F | 59.8°F | 4.34 | 14 | 1 | 1 | 14 h 30 min |
| June | 81°F | 59°F | 69.7°F | 3.65 | 12 | 4 | <1 | 15 h 10 min |
| July | 84°F | 63°F | 73.7°F | 3.62 | 10 | 6 | <1 | 15 h |
| August | 82°F | 62°F | 71.9°F | 3.84 | 11 | 3 | <1 | 14 h |
| September | 76°F | 54°F | 64.6°F | 3.00 | 10 | 2 | <1 | 12 h 30 min |
| October | 62°F | 42°F | 52.2°F | 2.99 | 11 | <1 | 5 | 11 h 10 min |
| November | 48°F | 31°F | 39.4°F | 2.20 | 9 | <1 | 17 | 9 h 50 min |
| December | 35°F | 21°F | 28.4°F | 1.67 | 9 | <1 | 27 | 9 h 10 min |
| Year (annual) | 59°F | 40°F | 49.7°F | 33.23 | 121 | 15 | 134 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −9°C | −4.8°C | 32 mm |
| February | 2°C | −7°C | −2.8°C | 31 mm |
| March | 8°C | −2°C | 3.2°C | 50 mm |
| April | 15°C | 3°C | 9.3°C | 87 mm |
| May | 22°C | 9°C | 15.4°C | 110 mm |
| June | 27°C | 15°C | 20.9°C | 93 mm |
| July | 29°C | 17°C | 23.2°C | 92 mm |
| August | 28°C | 17°C | 22.2°C | 98 mm |
| September | 24°C | 12°C | 18.1°C | 76 mm |
| October | 17°C | 6°C | 11.2°C | 76 mm |
| November | 9°C | 0°C | 4.1°C | 56 mm |
| December | 2°C | −6°C | −2.0°C | 42 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Streamwood (8 miles away), gets 34 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094892; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit West Chicago?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (10).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094892.
When is the last frost in West Chicago?
In West Chicago, the last spring frost (32°F) comes after April 25 in half of years and after May 12 in one year in ten; the first autumn frost comes before October 19 in half of years and before October 5 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 251 year in 10 after May 12; 9 in 10 after April 11
- First autumn frost, half of years before
- October 191 year in 10 before October 5; 9 in 10 before October 30
NOAA puts the median frost-free season at 174 days, and the season without a hard freeze (28°F) at 197 days.
A hard freeze (28°F) comes after April 14 in half of springs and before October 29 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts West Chicago in zone 5b in ZIP code 60185. By the map's own method, the average of each year's coldest night over 1991-2020, West Chicago's NOAA station is in zone 5b: the coldest night of a typical year reaches −12°F (23 complete years).
Frost dates for every NOAA station in Illinois · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00094892; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in West Chicago?
In a normal year in West Chicago, 15 days a year reach 90°F, 134 nights fall to 32°F or colder and 121 days bring measurable precipitation.
- Days at 90°F or more
- 15a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 134a normal year
- Days that stay below freezing
- 45high of 32°F or less
- Days with 0.01 inch of precipitation
- 121a normal year
The highest temperature in this station's record (since 1997) is 100°F, on July 24, 2005; the lowest is −29°F, on January 31, 2019.
The wettest calendar year on that record is 2019, with 43.26 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00094892; records: ACIS (NOAA Regional Climate Centers), station USW00094892. Records use complete months only; a month missing more than three days is left out.
How humid and windy is West Chicago, and how clear are its skies?
The summer (June-August) dew point averages 61°F. The muggiest month is July, with an average dew point of 62°F; the driest air comes in January (17°F). March is the windiest month (11.0 mph on average), and August has the most clear or nearly clear hours (74%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 17°F | 75% | 67% | 10.4 mph | 50% | 39% |
| February | 23°F | 72% | 59% | 10.8 mph | 49% | 40% |
| March | 32°F | 66% | 49% | 11.0 mph | 53% | 31% |
| April | 42°F | 64% | 49% | 10.5 mph | 57% | 27% |
| May | 53°F | 67% | 51% | 9.0 mph | 64% | 20% |
| June | 61°F | 69% | 52% | 8.0 mph | 72% | 10% |
| July | 62°F | 71% | 53% | 7.0 mph | 73% | 9% |
| August | 60°F | 72% | 53% | 7.2 mph | 74% | 12% |
| September | 49°F | 70% | 50% | 8.5 mph | 69% | 18% |
| October | 37°F | 71% | 55% | 10.0 mph | 55% | 33% |
| November | 27°F | 76% | 66% | 10.3 mph | 50% | 40% |
| December | 19°F | 78% | 69% | 10.6 mph | 49% | 43% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00094892. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is West Chicago?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around West Chicago, 3.9 kWh per square metre a day. July is the sunniest month (81%) and January the cloudiest (61%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 61% | 1.7 |
| February | 65% | 2.6 |
| March | 67% | 3.6 |
| April | 70% | 4.8 |
| May | 71% | 5.5 |
| June | 77% | 6.1 |
| July | 81% | 6.2 |
| August | 80% | 5.4 |
| September | 80% | 4.5 |
| October | 71% | 3.0 |
| November | 67% | 2.0 |
| December | 61% | 1.5 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does West Chicago need?
A normal year in West Chicago brings 6,364 heating degree days, 18% more than the median U.S. place (5,373), and 822 cooling degree days, 9% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,059 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,293 | 0 |
| February | 1,065 | 0 |
| March | 850 | 2 |
| April | 492 | 5 |
| May | 211 | 50 |
| June | 33 | 175 |
| July | 4 | 272 |
| August | 7 | 221 |
| September | 100 | 88 |
| October | 407 | 11 |
| November | 768 | 0 |
| December | 1,135 | 0 |
| Year (annual) | 6,364 | 822 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094892. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has West Chicago been warmer than normal lately?
2025 averaged 50.8°F, 1.1°F above the 1991-2020 normal of 49.7°F. 3 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 51.2°F | +1.5°F | 25.36 |
| 2022 | 49.4°F | −0.3°F | 31.75 |
| 2023 | 51.7°F | +2.0°F | 30.92 |
| 2025 | 50.8°F | +1.1°F | 27.11 |
Over 32 complete years from 1974 to 2025, the station's annual mean temperature rose at a fitted 2.9°F per century (+0.16°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00094892; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does West Chicago's climate compare?
West Chicago is warmer than 31 of the other 143 places with their own NOAA record in Illinois, and wetter than 1. Across the 7,247 U.S. stations with normals, its annual mean of 49.7°F is warmer than 39%.
In the Köppen classification computed from these normals, West Chicago is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near West Chicago share this climate record?
7 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Carol Stream, IL39,556 people · 6 mi E
- St. Charles, IL33,482 people · 3 mi W
- Geneva, IL21,168 people · 5 mi SW
- Campton Hills, IL10,894 people · 9 mi W
- Winfield, IL10,199 people · 5 mi SE
- Wayne, IL2,285 people · 2 mi N
- Lily Lake, IL1,059 people · 12 mi W
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about West Chicago's climate
What is the coldest month in West Chicago?
January, with a normal high of 31°F and a normal low of 16°F. The warmest is July (84°F by day, 63°F at night).
Does it snow in West Chicago?
Yes. NOAA publishes no 1991-2020 snowfall normal for West Chicago's NOAA station; the nearest record that keeps one, Streamwood (8 miles away), records 34 inches of snow in a normal year.
What is the rainiest month in West Chicago?
May, with 4.34 in of precipitation in a normal year; the driest is February with 1.24 in.
What plant hardiness zone is West Chicago in?
The USDA's 2023 map puts West Chicago in zone 5b in ZIP code 60185. By the same method at West Chicago's NOAA station, the coldest night of a typical year reaches −12°F (23 years, 1991-2020): zone 5b.
How late can frost come in West Chicago?
In half of years the last 32°F night comes after April 25; in one year in ten it comes after May 12. Waiting until May 12 leaves about a one-in-ten chance of a later frost.
Nearby and next
- West Chicago in OctoberThis month day by day, its records and recent years
- Illinois climateThe statewide normals and every place in the state
- Streamwood, IL9 miles from this station, 49.6°F a year
- Aurora, IL10 miles from this station, 50.2°F a year
- Elgin, IL11 miles from this station, 49.0°F a year
- Lisle, IL11 miles from this station, 49.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made