La Harpe, Illinois climate: Normal weather by month, frost dates and records
La Harpe's normal year runs from 15°F January nights to 85°F July afternoons, with 39.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.4°C, January lows of −9°C, July highs of 29°C, 993 mm of precipitation a year.
- NOAA stationLa Harpe
- Station IDUSC00114823
- Location40.58°N 90.97°W
- Elevation690 ft (210 m)
- From the centerunder 1 mile
- Population1,137
On October 23, the normal high in La Harpe is 61°F and the normal low 40°F, and the chance of measurable rain or snow is 24%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for La Harpe.
- Jan 32° 15°
- Feb 37° 19°
- Mar 49° 29°
- Apr 62° 40°
- May 72° 52°
- Jun 81° 61°
- Jul 85° 65°
- Aug 83° 63°
- Sep 77° 54°
- Oct 64° 42°
- Nov 49° 31°
- Dec 37° 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 La Harpe each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 15°F. The most precipitation falls in May (5.22 in), the least in January (1.60 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 32°F | 15°F | 23.3°F | 1.60 | 6 | <1 | 29 | 9 h 30 min |
| February | 37°F | 19°F | 27.8°F | 1.83 | 6 | <1 | 25 | 10 h 40 min |
| March | 49°F | 29°F | 39.3°F | 2.42 | 7 | <1 | 21 | 11 h 50 min |
| April | 62°F | 40°F | 50.9°F | 3.92 | 9 | <1 | 7 | 13 h 10 min |
| May | 72°F | 52°F | 62.0°F | 5.22 | 11 | 1 | <1 | 14 h 20 min |
| June | 81°F | 61°F | 71.2°F | 4.94 | 9 | 5 | <1 | 15 h |
| July | 85°F | 65°F | 74.6°F | 4.23 | 8 | 9 | <1 | 14 h 50 min |
| August | 83°F | 63°F | 72.8°F | 3.42 | 7 | 6 | <1 | 13 h 50 min |
| September | 77°F | 54°F | 65.3°F | 3.83 | 7 | 3 | <1 | 12 h 30 min |
| October | 64°F | 42°F | 53.2°F | 3.10 | 7 | <1 | 6 | 11 h 10 min |
| November | 49°F | 31°F | 39.9°F | 2.54 | 6 | <1 | 18 | 10 h |
| December | 37°F | 21°F | 28.9°F | 2.05 | 6 | <1 | 27 | 9 h 20 min |
| Year (annual) | 61°F | 41°F | 50.8°F | 39.10 | 90 | 24 | 134 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 0°C | −9°C | −4.8°C | 41 mm |
| February | 3°C | −7°C | −2.3°C | 46 mm |
| March | 10°C | −1°C | 4.1°C | 61 mm |
| April | 17°C | 4°C | 10.5°C | 100 mm |
| May | 22°C | 11°C | 16.7°C | 133 mm |
| June | 27°C | 16°C | 21.8°C | 125 mm |
| July | 29°C | 18°C | 23.7°C | 107 mm |
| August | 28°C | 17°C | 22.7°C | 87 mm |
| September | 25°C | 12°C | 18.5°C | 97 mm |
| October | 18°C | 6°C | 11.8°C | 79 mm |
| November | 10°C | −1°C | 4.4°C | 65 mm |
| December | 3°C | −6°C | −1.7°C | 52 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Burlington (2 mi S) (15 miles away), gets 22 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114823; 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 La Harpe?
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 (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 USC00114823.
When is the last frost in La Harpe?
In La Harpe, the last spring frost (32°F) comes after April 21 in half of years and after May 5 in one year in ten; the first autumn frost comes before October 19 in half of years and before October 4 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 211 year in 10 after May 5; 9 in 10 after April 6
- First autumn frost, half of years before
- October 191 year in 10 before October 4; 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 201 days.
A hard freeze (28°F) comes after April 8 in half of springs and before October 28 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts La Harpe in zone 6a in ZIP code 61450, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, La Harpe's NOAA station is in zone 5b: the coldest night of a typical year reaches −11°F (26 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Illinois · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00114823; 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 La Harpe?
In a normal year in La Harpe, 24 days a year reach 90°F, 134 nights fall to 32°F or colder and 90 days bring measurable precipitation.
- Days at 90°F or more
- 24a 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
- 39high of 32°F or less
- Days with 0.01 inch of precipitation
- 90a normal year
The highest temperature in this station's record (since 1895) is 113°F, on August 9, 1934; the lowest is −30°F, on February 13, 1905.
The wettest calendar year on that record is 2010, with 52.81 in; the snowiest season is 1978–79, with 51.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00114823; records: ACIS (NOAA Regional Climate Centers), station USC00114823. Records use complete months only; a month missing more than three days is left out.
How sunny is La Harpe?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around La Harpe, 4.1 kWh per square metre a day. July is the sunniest month (82%) and January the cloudiest (63%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 63% | 1.9 |
| February | 68% | 2.8 |
| March | 68% | 3.8 |
| April | 70% | 4.9 |
| May | 73% | 5.6 |
| June | 79% | 6.3 |
| July | 82% | 6.4 |
| August | 81% | 5.5 |
| September | 82% | 4.7 |
| October | 73% | 3.2 |
| November | 70% | 2.2 |
| December | 63% | 1.6 |
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 La Harpe need?
A normal year in La Harpe brings 6,103 heating degree days, 14% more than the median U.S. place (5,373), and 955 cooling degree days, 5% 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 3,336 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,291 | 0 |
| February | 1,042 | 0 |
| March | 798 | 2 |
| April | 433 | 9 |
| May | 161 | 68 |
| June | 21 | 207 |
| July | 2 | 301 |
| August | 6 | 248 |
| September | 96 | 106 |
| October | 381 | 15 |
| November | 753 | 0 |
| December | 1,119 | 0 |
| Year (annual) | 6,103 | 955 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114823. 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 La Harpe been warmer than normal lately?
2024 averaged 53.9°F, 3.1°F above the 1991-2020 normal of 50.8°F. 3 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 51.9°F | +1.1°F | 38.58 |
| 2022 | 49.7°F | −1.1°F | 27.11 |
| 2023 | 53.0°F | +2.2°F | 29.06 |
| 2024 | 53.9°F | +3.1°F | 36.98 |
Over 108 complete years from 1897 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 USC00114823; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does La Harpe's climate compare?
La Harpe is warmer than 49 of the other 143 places with their own NOAA record in Illinois, and wetter than 55. Across the 7,247 U.S. stations with normals, its annual mean of 50.8°F is warmer than 44%.
In the Köppen classification computed from these normals, La Harpe 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 La Harpe 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.
- Colchester, IL1,082 people · 14 mi SE
- Blandinsville, IL550 people · 6 mi E
- Wever, IA190 people · 16 mi NW
- Tennessee, IL100 people · 14 mi SE
- Sciota, IL36 people · 12 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 La Harpe's climate
What is the coldest month in La Harpe?
January, with a normal high of 32°F and a normal low of 15°F. The warmest is July (85°F by day, 65°F at night).
Does it snow in La Harpe?
Yes. NOAA publishes no 1991-2020 snowfall normal for La Harpe's NOAA station; the nearest record that keeps one, Burlington (2 mi S) (15 miles away), records 22 inches of snow in a normal year.
What is the rainiest month in La Harpe?
May, with 5.22 in of precipitation in a normal year; the driest is January with 1.60 in.
What plant hardiness zone is La Harpe in?
The USDA's 2023 map puts La Harpe in zone 6a in ZIP code 61450, the nearest ZIP area. By the same method at La Harpe's NOAA station, the coldest night of a typical year reaches −11°F (26 years, 1991-2020): zone 5b.
How late can frost come in La Harpe?
In half of years the last 32°F night comes after April 21; in one year in ten it comes after May 5. Waiting until May 5 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Burlington, IA16 miles from this station, 51.9°F a year
- Bentley, IL18 miles from this station, 52.8°F a year
- Fort Madison, IA19 miles from this station, 52.2°F a year
- Gladstone, IL21 miles from this station, 51.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made