Walnut, Illinois climate: Normal weather by month, frost dates and records
Walnut's normal year runs from 13°F January nights to 83°F July afternoons, with 36.8 inches of precipitation and 36 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.6°C, January lows of −11°C, July highs of 29°C, 936 mm of precipitation a year.
- NOAA stationWalnut
- Station IDUSC00118916
- Location41.56°N 89.60°W
- Elevation671 ft (205 m)
- From the centerunder 1 mile
- Population1,265
On October 23, the normal high in Walnut is 60°F and the normal low 39°F, and the chance of measurable rain or snow is 20%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Walnut.
- Jan 29° 13°
- Feb 34° 17°
- Mar 47° 28°
- Apr 61° 39°
- May 72° 51°
- Jun 81° 60°
- Jul 83° 63°
- Aug 82° 61°
- Sep 76° 53°
- Oct 63° 41°
- Nov 48° 30°
- Dec 35° 19°
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 Walnut each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 13°F. The most precipitation falls in June (4.93 in), the least in January (1.52 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 29°F | 13°F | 21.1°F | 1.52 | 12.7 | 6 | <1 | 30 | 9 h 30 min |
| February | 34°F | 17°F | 25.4°F | 1.73 | 8.4 | 5 | <1 | 26 | 10 h 40 min |
| March | 47°F | 28°F | 37.5°F | 2.22 | 4.7 | 7 | <1 | 22 | 11 h 50 min |
| April | 61°F | 39°F | 49.5°F | 3.35 | 0.6 | 8 | <1 | 7 | 13 h 20 min |
| May | 72°F | 51°F | 61.1°F | 4.63 | 0.0 | 10 | 1 | <1 | 14 h 30 min |
| June | 81°F | 60°F | 70.5°F | 4.93 | 0.0 | 8 | 4 | <1 | 15 h 10 min |
| July | 83°F | 63°F | 73.4°F | 3.94 | 0.0 | 7 | 5 | <1 | 15 h |
| August | 82°F | 61°F | 71.3°F | 3.83 | 0.0 | 7 | 3 | <1 | 13 h 50 min |
| September | 76°F | 53°F | 64.4°F | 3.40 | 0.0 | 6 | 2 | <1 | 12 h 30 min |
| October | 63°F | 41°F | 52.1°F | 2.97 | 0.2 | 7 | <1 | 6 | 11 h 10 min |
| November | 48°F | 30°F | 38.7°F | 2.33 | 2.0 | 6 | <1 | 18 | 9 h 50 min |
| December | 35°F | 19°F | 27.1°F | 1.99 | 7.3 | 6 | <1 | 28 | 9 h 10 min |
| Year (annual) | 59°F | 40°F | 49.3°F | 36.84 | 35.9 | 83 | 14 | 136 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −11°C | −6.1°C | 39 mm | 32 cm |
| February | 1°C | −8°C | −3.7°C | 44 mm | 21 cm |
| March | 8°C | −2°C | 3.1°C | 56 mm | 12 cm |
| April | 16°C | 4°C | 9.7°C | 85 mm | 2 cm |
| May | 22°C | 10°C | 16.2°C | 118 mm | 0 cm |
| June | 27°C | 16°C | 21.4°C | 125 mm | 0 cm |
| July | 29°C | 17°C | 23.0°C | 100 mm | 0 cm |
| August | 28°C | 16°C | 21.8°C | 97 mm | 0 cm |
| September | 24°C | 12°C | 18.0°C | 86 mm | 0 cm |
| October | 17°C | 5°C | 11.2°C | 75 mm | 1 cm |
| November | 9°C | −1°C | 3.7°C | 59 mm | 5 cm |
| December | 2°C | −7°C | −2.7°C | 51 mm | 19 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00118916; 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 Walnut?
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 (6).
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 USC00118916.
When is the last frost in Walnut?
In Walnut, the last spring frost (32°F) comes after April 24 in half of years and after May 9 in one year in ten; the first autumn frost comes before October 14 in half of years and before September 30 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 241 year in 10 after May 9; 9 in 10 after April 10
- First autumn frost, half of years before
- October 141 year in 10 before September 30; 9 in 10 before October 27
NOAA puts the median frost-free season at 172 days, and the season without a hard freeze (28°F) at 193 days.
A hard freeze (28°F) comes after April 12 in half of springs and before October 24 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Walnut in zone 5b in ZIP code 61376, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Walnut's NOAA station is in zone 5b: the coldest night of a typical year reaches −14°F (28 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 USC00118916; 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 Walnut?
In a normal year in Walnut, 14 days a year reach 90°F, 136 nights fall to 32°F or colder and 83 days bring measurable precipitation.
- Days at 90°F or more
- 14a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 136a normal year
- Days that stay below freezing
- 48high of 32°F or less
- Days with 0.01 inch of precipitation
- 83a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in this station's record (since 1893) is 111°F, on July 14, 1936; the lowest is −27°F, on January 20, 1985.
The wettest calendar year on that record is 2019, with 53.88 in; the snowiest season is 1978–79, with 69.4 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00118916; records: ACIS (NOAA Regional Climate Centers), station USC00118916. Records use complete months only; a month missing more than three days is left out.
How sunny is Walnut?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Walnut, 4.0 kWh per square metre a day. July is the sunniest month (81%) and December the cloudiest (63%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 64% | 1.8 |
| February | 68% | 2.7 |
| March | 68% | 3.7 |
| April | 70% | 4.8 |
| May | 72% | 5.5 |
| June | 77% | 6.2 |
| July | 81% | 6.3 |
| August | 80% | 5.5 |
| September | 80% | 4.5 |
| October | 72% | 3.0 |
| November | 68% | 2.0 |
| December | 63% | 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 Walnut need?
A normal year in Walnut brings 6,510 heating degree days, 21% more than the median U.S. place (5,373), and 841 cooling degree days, 7% 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 3,113 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,361 | 0 |
| February | 1,107 | 0 |
| March | 854 | 0 |
| April | 472 | 9 |
| May | 185 | 65 |
| June | 27 | 191 |
| July | 5 | 264 |
| August | 12 | 207 |
| September | 109 | 92 |
| October | 413 | 13 |
| November | 789 | 0 |
| December | 1,176 | 0 |
| Year (annual) | 6,510 | 841 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00118916. 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 Walnut been warmer than normal lately?
2023 averaged 51.9°F, 2.6°F above the 1991-2020 normal of 49.3°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 51.0°F | +1.7°F | 31.29 | 29.5 |
| 2022 | 48.7°F | −0.6°F | 33.16 | 24.0 |
| 2023 | 51.9°F | +2.6°F | – | – |
Over 101 complete years from 1893 to 2025, the station's annual mean temperature rose at a fitted 1.5°F per century (+0.09°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00118916; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Walnut's climate compare?
Walnut is warmer than 21 of the other 143 places with their own NOAA record in Illinois, and wetter than 12. Across the 7,247 U.S. stations with normals, its annual mean of 49.3°F is warmer than 37%.
In the Köppen classification computed from these normals, Walnut 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 Walnut share this climate record?
5 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.
- Tampico, IL675 people · 11 mi NW
- Ohio, IL458 people · 7 mi E
- Manlius, IL290 people · 8 mi SW
- New Bedford, IL75 people · 7 mi SW
- Deer Grove, IL39 people · 6 mi NW
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 Walnut's climate
What is the coldest month in Walnut?
January, with a normal high of 29°F and a normal low of 13°F. The warmest is July (83°F by day, 63°F at night).
Does it snow in Walnut?
Yes: 36 inches in a normal year, falling on 14 days with 0.1 inch or more, the most in January (12.7 inches).
What is the rainiest month in Walnut?
June, with 4.93 in of precipitation in a normal year; the driest is January with 1.52 in.
What plant hardiness zone is Walnut in?
The USDA's 2023 map puts Walnut in zone 5b in ZIP code 61376, the nearest ZIP area. By the same method at Walnut's NOAA station, the coldest night of a typical year reaches −14°F (28 years, 1991-2020): zone 5b.
How late can frost come in Walnut?
In half of years the last 32°F night comes after April 24; in one year in ten it comes after May 9. Waiting until May 9 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Princeton, IL16 miles from this station, 49.7°F a year
- Dixon, IL19 miles from this station, 49.4°F a year
- Morrison, IL25 miles from this station, 48.3°F a year
- Hennepin, IL25 miles from this station, 51.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made