Geneseo, Illinois climate: Normal weather by month, frost dates and records
Geneseo's normal year runs from 15°F January nights to 86°F July afternoons, with 39.1 inches of precipitation and 28 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.5°C, January lows of −10°C, July highs of 30°C, 993 mm of precipitation a year.
- NOAA stationGeneseo
- Station IDUSC00113384
- Location41.45°N 90.15°W
- Elevation639 ft (195 m)
- From the centerunder 1 mile
- Population6,503
On October 23, the normal high in Geneseo is 61°F and the normal low 40°F, and the chance of measurable rain or snow is 28%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Geneseo.
- Jan 31° 15°
- Feb 36° 19°
- Mar 49° 29°
- Apr 62° 40°
- May 74° 52°
- Jun 83° 62°
- Jul 86° 65°
- Aug 83° 63°
- Sep 77° 55°
- Oct 64° 43°
- Nov 49° 31°
- Dec 36° 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 Geneseo each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 15°F. The most precipitation falls in May (4.87 in), the least in January (1.64 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 31°F | 15°F | 22.7°F | 1.64 | 9.8 | 8 | <1 | 29 | 9 h 30 min |
| February | 36°F | 19°F | 27.2°F | 1.81 | 6.1 | 7 | <1 | 25 | 10 h 40 min |
| March | 49°F | 29°F | 39.1°F | 2.70 | 2.8 | 9 | <1 | 20 | 11 h 50 min |
| April | 62°F | 40°F | 51.1°F | 3.96 | 0.7 | 11 | <1 | 5 | 13 h 20 min |
| May | 74°F | 52°F | 62.6°F | 4.87 | 0.0 | 12 | 1 | <1 | 14 h 30 min |
| June | 83°F | 62°F | 72.2°F | 4.42 | 0.0 | 10 | 5 | <1 | 15 h 10 min |
| July | 86°F | 65°F | 75.4°F | 4.13 | 0.0 | 8 | 8 | <1 | 14 h 50 min |
| August | 83°F | 63°F | 73.1°F | 4.10 | 0.0 | 9 | 5 | <1 | 13 h 50 min |
| September | 77°F | 55°F | 65.8°F | 3.57 | 0.0 | 8 | 2 | <1 | 12 h 30 min |
| October | 64°F | 43°F | 53.4°F | 3.21 | 0.1 | 9 | <1 | 3 | 11 h 10 min |
| November | 49°F | 31°F | 39.8°F | 2.56 | 1.6 | 8 | <1 | 17 | 9 h 50 min |
| December | 36°F | 21°F | 28.2°F | 2.12 | 7.3 | 8 | <1 | 27 | 9 h 10 min |
| Year (annual) | 61°F | 41°F | 50.9°F | 39.09 | 28.4 | 108 | 22 | 126 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −10°C | −5.2°C | 42 mm | 25 cm |
| February | 2°C | −7°C | −2.7°C | 46 mm | 15 cm |
| March | 9°C | −1°C | 3.9°C | 69 mm | 7 cm |
| April | 17°C | 4°C | 10.6°C | 101 mm | 2 cm |
| May | 23°C | 11°C | 17.0°C | 124 mm | 0 cm |
| June | 28°C | 16°C | 22.3°C | 112 mm | 0 cm |
| July | 30°C | 18°C | 24.1°C | 105 mm | 0 cm |
| August | 29°C | 17°C | 22.8°C | 104 mm | 0 cm |
| September | 25°C | 13°C | 18.8°C | 91 mm | 0 cm |
| October | 18°C | 6°C | 11.9°C | 82 mm | 0 cm |
| November | 9°C | −1°C | 4.3°C | 65 mm | 4 cm |
| December | 2°C | −6°C | −2.1°C | 54 mm | 19 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00113384; 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 Geneseo?
Normal highs sit between 65°F and 85°F in May, June, August and September. Of those, September has the fewest days with rain (8).
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 USC00113384.
When is the last frost in Geneseo?
In Geneseo, the last spring frost (32°F) comes after April 20 in half of years and after May 6 in one year in ten; the first autumn frost comes before October 20 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 201 year in 10 after May 6; 9 in 10 after April 6
- First autumn frost, half of years before
- October 201 year in 10 before October 5; 9 in 10 before October 31
NOAA puts the median frost-free season at 180 days, and the season without a hard freeze (28°F) at 202 days.
A hard freeze (28°F) comes after April 9 in half of springs and before October 30 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Geneseo in zone 5b in ZIP code 61254, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Geneseo's NOAA station is in zone 5b: the coldest night of a typical year reaches −11°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 USC00113384; 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 Geneseo?
In a normal year in Geneseo, 22 days a year reach 90°F (1 of them 100°F or more), 126 nights fall to 32°F or colder and 108 days bring measurable precipitation.
- Days at 90°F or more
- 22a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 126a normal year
- Days that stay below freezing
- 45high of 32°F or less
- Days with 0.01 inch of precipitation
- 108a normal year
- Days with 1 inch of snow or more
- 10a normal year
The highest temperature in this station's record (since 1895) is 107°F, on July 24, 1901; the lowest is −25°F, on January 31, 2019.
The wettest calendar year on that record is 2019, with 54.72 in; the snowiest season is 1978–79, with 52.9 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00113384; records: ACIS (NOAA Regional Climate Centers), station USC00113384. Records use complete months only; a month missing more than three days is left out.
How sunny is Geneseo?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Geneseo, 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 | 70% | 2.8 |
| March | 69% | 3.7 |
| April | 70% | 4.8 |
| May | 72% | 5.5 |
| June | 77% | 6.2 |
| July | 81% | 6.3 |
| August | 80% | 5.5 |
| September | 81% | 4.5 |
| October | 72% | 3.0 |
| November | 69% | 2.1 |
| 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 Geneseo need?
A normal year in Geneseo brings 6,139 heating degree days, 14% more than the median U.S. place (5,373), and 1,031 cooling degree days, 14% more 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 3,426 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,311 | 0 |
| February | 1,060 | 0 |
| March | 805 | 2 |
| April | 428 | 10 |
| May | 152 | 79 |
| June | 16 | 231 |
| July | 2 | 324 |
| August | 5 | 258 |
| September | 87 | 111 |
| October | 375 | 17 |
| November | 758 | 1 |
| December | 1,141 | 0 |
| Year (annual) | 6,139 | 1,031 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00113384. 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 Geneseo been warmer than normal lately?
2025 averaged 52.1°F, 1.2°F above the 1991-2020 normal of 50.9°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 51.8°F | +0.9°F | 41.07 | 13.5 |
| 2022 | 49.8°F | −1.1°F | 36.54 | 17.1 |
| 2023 | 53.0°F | +2.1°F | 34.48 | 14.0 |
| 2024 | 53.8°F | +2.9°F | 35.88 | 24.0 |
| 2025 | 52.1°F | +1.2°F | 32.95 | – |
Over 81 complete years from 1896 to 2025, the station's annual mean temperature rose at a fitted 2.0°F per century (+0.11°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00113384; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Geneseo's climate compare?
Geneseo is warmer than 54 of the other 143 places with their own NOAA record in Illinois, and wetter than 54. Across the 7,247 U.S. stations with normals, its annual mean of 50.9°F is warmer than 44%.
In the Köppen classification computed from these normals, Geneseo 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 Geneseo share this climate record?
3 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.
- Cambridge, IL2,034 people · 11 mi S
- Atkinson, IL930 people · 8 mi E
- Hooppole, IL173 people · 13 mi E
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 Geneseo's climate
What is the coldest month in Geneseo?
January, with a normal high of 31°F and a normal low of 15°F. The warmest is July (86°F by day, 65°F at night).
Does it snow in Geneseo?
Yes: 28 inches in a normal year, falling on 14 days with 0.1 inch or more, the most in January (9.8 inches).
What is the rainiest month in Geneseo?
May, with 4.87 in of precipitation in a normal year; the driest is January with 1.64 in.
What plant hardiness zone is Geneseo in?
The USDA's 2023 map puts Geneseo in zone 5b in ZIP code 61254, the nearest ZIP area. By the same method at Geneseo's NOAA station, the coldest night of a typical year reaches −11°F (30 years, 1991-2020): zone 5b.
How late can frost come in Geneseo?
In half of years the last 32°F night comes after April 20; in one year in ten it comes after May 6. Waiting until May 6 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Le Claire, IA16 miles from this station, 50.6°F a year
- Kewanee, IL19 miles from this station, 49.6°F a year
- Moline, IL19 miles from this station, 51.2°F a year
- Galva, IL20 miles from this station, 49.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made