Altona, Illinois climate: Normal weather by month, frost dates and records
Altona's normal year runs from 13°F January nights to 83°F July afternoons, with 39.4 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.4°C, January lows of −11°C, July highs of 29°C, 1,000 mm of precipitation a year.
- NOAA stationAltona
- Station IDUSC00110140
- Location41.12°N 90.16°W
- Elevation765 ft (233 m)
- From the centerunder 1 mile
- Population451
On October 23, the normal high in Altona is 61°F and the normal low 37°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Altona.
- Jan 30° 13°
- Feb 35° 16°
- Mar 48° 27°
- Apr 62° 37°
- May 72° 49°
- Jun 81° 59°
- Jul 83° 62°
- Aug 82° 59°
- Sep 76° 52°
- Oct 64° 40°
- Nov 49° 28°
- 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 Altona 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 May (5.21 in), the least in January (1.82 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 30°F | 13°F | 21.4°F | 1.82 | – | <1 | 29 | 9 h 30 min |
| February | 35°F | 16°F | 25.5°F | 2.07 | – | <1 | 27 | 10 h 40 min |
| March | 48°F | 27°F | 37.3°F | 2.58 | – | <1 | 22 | 11 h 50 min |
| April | 62°F | 37°F | 49.2°F | 4.00 | – | <1 | 11 | 13 h 20 min |
| May | 72°F | 49°F | 60.6°F | 5.21 | – | 1 | 1 | 14 h 30 min |
| June | 81°F | 59°F | 69.7°F | 4.72 | – | 3 | <1 | 15 h 10 min |
| July | 83°F | 62°F | 72.6°F | 3.98 | – | 6 | <1 | 14 h 50 min |
| August | 82°F | 59°F | 70.6°F | 3.76 | – | 3 | <1 | 13 h 50 min |
| September | 76°F | 52°F | 64.0°F | 3.81 | – | 2 | <1 | 12 h 30 min |
| October | 64°F | 40°F | 51.9°F | 2.77 | – | <1 | 7 | 11 h 10 min |
| November | 49°F | 28°F | 38.3°F | 2.56 | – | <1 | 20 | 10 h |
| December | 35°F | 19°F | 27.1°F | 2.10 | – | <1 | 28 | 9 h 10 min |
| Year (annual) | 60°F | 38°F | 49.0°F | 39.38 | – | 16 | 144 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −11°C | −5.9°C | 46 mm |
| February | 2°C | −9°C | −3.6°C | 53 mm |
| March | 9°C | −3°C | 2.9°C | 66 mm |
| April | 16°C | 3°C | 9.6°C | 102 mm |
| May | 22°C | 10°C | 15.9°C | 132 mm |
| June | 27°C | 15°C | 20.9°C | 120 mm |
| July | 29°C | 17°C | 22.6°C | 101 mm |
| August | 28°C | 15°C | 21.4°C | 96 mm |
| September | 25°C | 11°C | 17.8°C | 97 mm |
| October | 18°C | 4°C | 11.1°C | 70 mm |
| November | 9°C | −2°C | 3.5°C | 65 mm |
| December | 2°C | −7°C | −2.7°C | 53 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Kewanee (16 miles away), gets 31 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00110140; 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 Altona?
Normal highs sit between 65°F and 85°F in May, June, July, August and September.
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 USC00110140.
When is the last frost in Altona?
In Altona, the last spring frost (32°F) comes after April 28 in half of years and after May 12 in one year in ten; the first autumn frost comes before October 12 in half of years and before September 28 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 281 year in 10 after May 12; 9 in 10 after April 15
- First autumn frost, half of years before
- October 121 year in 10 before September 28; 9 in 10 before October 26
NOAA puts the median frost-free season at 165 days, and the season without a hard freeze (28°F) at 185 days.
A hard freeze (28°F) comes after April 18 in half of springs and before October 22 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Altona in zone 5b in ZIP code 61414, the nearest ZIP area.
Frost dates for every NOAA station in Illinois · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00110140; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 Altona?
In a normal year in Altona, 16 days a year reach 90°F and 144 nights fall to 32°F or colder.
- Days at 90°F or more
- 16a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 144a normal year
- Days that stay below freezing
- 47high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00110140.
How sunny is Altona?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Altona, 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 Altona need?
A normal year in Altona brings 6,534 heating degree days, 22% more than the median U.S. place (5,373), and 744 cooling degree days, 18% 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 3,005 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,350 | 0 |
| February | 1,105 | 0 |
| March | 860 | 1 |
| April | 478 | 4 |
| May | 188 | 52 |
| June | 23 | 164 |
| July | 8 | 243 |
| August | 12 | 186 |
| September | 114 | 82 |
| October | 419 | 11 |
| November | 801 | 0 |
| December | 1,176 | 0 |
| Year (annual) | 6,534 | 744 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00110140. 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 Altona been warmer than normal lately?
2023 averaged 52.2°F, 3.2°F above the 1991-2020 normal of 49.0°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 51.2°F | +2.2°F | – |
| 2022 | 48.5°F | −0.5°F | 34.01 |
| 2023 | 52.2°F | +3.2°F | 36.82 |
Source: observed years: ACIS, station USC00110140. A year counts only with all twelve months complete.
How does Altona's climate compare?
Altona is warmer than 17 of the other 143 places with their own NOAA record in Illinois, and wetter than 60. Across the 7,247 U.S. stations with normals, its annual mean of 49.0°F is warmer than 36%.
In the Köppen classification computed from these normals, Altona 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 Altona 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.
- Woodhull, IL733 people · 9 mi NW
- Oneida, IL681 people · 5 mi SW
- Alpha, IL653 people · 12 mi NW
- Victoria, IL259 people · 7 mi SE
- Nekoma, IL54 people · 4 mi N
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 Altona's climate
What is the coldest month in Altona?
January, with a normal high of 30°F and a normal low of 13°F. The warmest is July (83°F by day, 62°F at night).
Does it snow in Altona?
Yes. NOAA publishes no 1991-2020 snowfall normal for Altona's NOAA station; the nearest record that keeps one, Kewanee (16 miles away), records 31 inches of snow in a normal year.
What is the rainiest month in Altona?
May, with 5.21 in of precipitation in a normal year; the driest is January with 1.82 in.
What plant hardiness zone is Altona in?
The USDA's 2023 map puts Altona in zone 5b in ZIP code 61414, the nearest ZIP area.
How late can frost come in Altona?
In half of years the last 32°F night comes after April 28; 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
- Illinois climateThe statewide normals and every place in the state
- Galva, IL7 miles from this station, 49.5°F a year
- Kewanee, IL16 miles from this station, 49.6°F a year
- Knoxville, IL16 miles from this station, 50.4°F a year
- Galesburg, IL17 miles from this station, 50.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made