Fairfield, Illinois climate: Normal weather by month, frost dates and records
Fairfield's normal year runs from 25°F January nights to 90°F July afternoons, with 46.0 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 13.9°C, January lows of −4°C, July highs of 32°C, 1,168 mm of precipitation a year.
- NOAA stationFairfield Radio WFIW
- Station IDUSC00112931
- Location38.38°N 88.33°W
- Elevation430 ft (131 m)
- From the center2 miles
- Population4,790
On October 14, the normal high in Fairfield is 72°F and the normal low 48°F, and the chance of measurable rain or snow is 26%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Fairfield.
- Jan 41° 25°
- Feb 47° 28°
- Mar 57° 36°
- Apr 69° 47°
- May 78° 56°
- Jun 87° 64°
- Jul 90° 68°
- Aug 89° 66°
- Sep 83° 58°
- Oct 71° 47°
- Nov 56° 36°
- Dec 45° 29°
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 Fairfield each month?
July is the warmest month, with normal highs of 90°F; January the coldest, with normal lows of 25°F. The most precipitation falls in April (5.00 in), the least in February (2.68 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 41°F | 25°F | 32.8°F | 3.33 | 9 | <1 | 25 | 9 h 50 min |
| February | 47°F | 28°F | 37.2°F | 2.68 | 8 | <1 | 20 | 10 h 40 min |
| March | 57°F | 36°F | 46.6°F | 4.22 | 11 | <1 | 14 | 11 h 50 min |
| April | 69°F | 47°F | 57.7°F | 5.00 | 11 | <1 | 3 | 13 h 10 min |
| May | 78°F | 56°F | 67.0°F | 4.98 | 12 | 1 | <1 | 14 h 10 min |
| June | 87°F | 64°F | 75.6°F | 4.70 | 10 | 9 | <1 | 14 h 50 min |
| July | 90°F | 68°F | 78.7°F | 3.83 | 9 | 15 | <1 | 14 h 40 min |
| August | 89°F | 66°F | 77.2°F | 3.51 | 7 | 12 | <1 | 13 h 40 min |
| September | 83°F | 58°F | 70.2°F | 2.90 | 7 | 6 | <1 | 12 h 30 min |
| October | 71°F | 47°F | 58.8°F | 3.73 | 8 | 1 | 3 | 11 h 20 min |
| November | 56°F | 36°F | 46.2°F | 3.82 | 9 | <1 | 13 | 10 h 10 min |
| December | 45°F | 29°F | 36.9°F | 3.30 | 10 | <1 | 21 | 9 h 30 min |
| Year (annual) | 68°F | 47°F | 57.1°F | 46.00 | 111 | 44 | 99 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 5°C | −4°C | 0.4°C | 85 mm |
| February | 8°C | −2°C | 2.9°C | 68 mm |
| March | 14°C | 2°C | 8.1°C | 107 mm |
| April | 21°C | 8°C | 14.3°C | 127 mm |
| May | 26°C | 13°C | 19.4°C | 126 mm |
| June | 31°C | 18°C | 24.2°C | 119 mm |
| July | 32°C | 20°C | 25.9°C | 97 mm |
| August | 32°C | 19°C | 25.1°C | 89 mm |
| September | 28°C | 14°C | 21.2°C | 74 mm |
| October | 21°C | 8°C | 14.9°C | 95 mm |
| November | 13°C | 2°C | 7.9°C | 97 mm |
| December | 7°C | −2°C | 2.7°C | 84 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Grayville (19 miles away), gets 12 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00112931; 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 Fairfield?
Normal highs sit between 65°F and 85°F in April, May, September and October. Of those, September has the fewest days with rain (7).
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 USC00112931.
When is the last frost in Fairfield?
In Fairfield, the last spring frost (32°F) comes after April 7 in half of years and after April 23 in one year in ten; the first autumn frost comes before October 26 in half of years and before October 14 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 71 year in 10 after April 23; 9 in 10 after March 23
- First autumn frost, half of years before
- October 261 year in 10 before October 14; 9 in 10 before November 9
NOAA puts the median frost-free season at 201 days, and the season without a hard freeze (28°F) at 224 days.
A hard freeze (28°F) comes after March 27 in half of springs and before November 6 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Fairfield in zone 6b in ZIP code 62837, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Fairfield's NOAA station is in zone 6b: the coldest night of a typical year reaches −2°F (30 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 USC00112931; 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 Fairfield?
In a normal year in Fairfield, 44 days a year reach 90°F (2 of them 100°F or more), 99 nights fall to 32°F or colder and 111 days bring measurable precipitation.
- Days at 90°F or more
- 44a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 99a normal year
- Days that stay below freezing
- 18high of 32°F or less
- Days with 0.01 inch of precipitation
- 111a normal year
The highest temperature in this station's record (since 1896) is 113°F, on July 22, 1901; the lowest is −23°F, on January 17, 1977.
The wettest calendar year on that record is 2019, with 68.81 in; the snowiest season is 1911–12, with 39.8 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00112931; records: ACIS (NOAA Regional Climate Centers), station USC00112931. Records use complete months only; a month missing more than three days is left out.
How sunny is Fairfield?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Fairfield, 4.2 kWh per square metre a day. August is the sunniest month (83%) and December the cloudiest (63%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 65% | 2.0 |
| February | 66% | 2.8 |
| March | 67% | 3.7 |
| April | 73% | 5.0 |
| May | 73% | 5.6 |
| June | 82% | 6.5 |
| July | 83% | 6.3 |
| August | 83% | 5.7 |
| September | 81% | 4.7 |
| October | 76% | 3.4 |
| November | 71% | 2.4 |
| December | 63% | 1.7 |
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 Fairfield need?
A normal year in Fairfield brings 4,398 heating degree days, 18% fewer than the median U.S. place (5,373), and 1,546 cooling degree days, 70% more than the median (908). Five months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 4,412 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 998 | 0 |
| February | 779 | 0 |
| March | 575 | 6 |
| April | 251 | 34 |
| May | 76 | 138 |
| June | 5 | 323 |
| July | 0 | 425 |
| August | 1 | 379 |
| September | 38 | 196 |
| October | 238 | 44 |
| November | 567 | 3 |
| December | 871 | 0 |
| Year (annual) | 4,398 | 1,546 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00112931. 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 Fairfield been warmer than normal lately?
2025 averaged 56.2°F, 0.9°F below the 1991-2020 normal of 57.1°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 57.4°F | +0.3°F | 45.96 |
| 2024 | 57.9°F | +0.8°F | 49.51 |
| 2025 | 56.2°F | −0.9°F | – |
Over 98 complete years from 1897 to 2025, the station's annual mean temperature rose at a fitted 0.5°F per century (+0.03°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00112931; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Fairfield's climate compare?
Fairfield is warmer than 138 of the other 143 places with their own NOAA record in Illinois, and wetter than 123. Across the 7,247 U.S. stations with normals, its annual mean of 57.1°F is warmer than 67%.
In the Köppen classification computed from these normals, Fairfield is Cfa: temperate, 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 Fairfield 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.
- Cisne, IL622 people · 11 mi NW
- Jeffersonville, IL350 people · 6 mi NW
- Mill Shoals, IL172 people · 9 mi S
- Sims, IL169 people · 11 mi W
- Mount Erie, IL95 people · 11 mi NE
- Golden Gate, IL62 people · 7 mi E
- Burnt Prairie, IL33 people · 10 mi S
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 Fairfield's climate
What is the coldest month in Fairfield?
January, with a normal high of 41°F and a normal low of 25°F. The warmest is July (90°F by day, 68°F at night).
Does it snow in Fairfield?
Yes. NOAA publishes no 1991-2020 snowfall normal for Fairfield's NOAA station; the nearest record that keeps one, Grayville (19 miles away), records 12 inches of snow in a normal year.
What is the rainiest month in Fairfield?
April, with 5.00 in of precipitation in a normal year; the driest is February with 2.68 in.
What plant hardiness zone is Fairfield in?
The USDA's 2023 map puts Fairfield in zone 6b in ZIP code 62837, the nearest ZIP area. By the same method at Fairfield's NOAA station, the coldest night of a typical year reaches −2°F (30 years, 1991-2020): zone 6b.
How late can frost come in Fairfield?
In half of years the last 32°F night comes after April 7; in one year in ten it comes after April 23. Waiting until April 23 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Albion, IL14 miles from this station, 56.6°F a year
- Grayville, IL19 miles from this station, 56.2°F a year
- Flora, IL22 miles from this station, 55.0°F a year
- Carmi, IL22 miles from this station, 55.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made