Mount Carroll, Illinois climate: Normal weather by month, frost dates and records
Mount Carroll's normal year runs from 11°F January nights to 85°F July afternoons, with 40.3 inches of precipitation and 33 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.2°C, January lows of −12°C, July highs of 29°C, 1,024 mm of precipitation a year.
- NOAA stationMount Carroll
- Station IDUSC00115901
- Location42.10°N 89.98°W
- Elevation640 ft (195 m)
- From the centerunder 1 mile
- Population1,433
On October 14, the normal high in Mount Carroll is 65°F and the normal low 39°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 Mount Carroll.
- Jan 31° 11°
- Feb 35° 14°
- Mar 48° 26°
- Apr 61° 36°
- May 72° 47°
- Jun 82° 57°
- Jul 85° 60°
- Aug 83° 58°
- Sep 77° 50°
- Oct 64° 38°
- Nov 49° 27°
- Dec 36° 17°
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 Mount Carroll each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 11°F. The most precipitation falls in June (5.49 in), the least in January (1.66 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 31°F | 11°F | 20.8°F | 1.66 | 10.2 | 9 | <1 | 30 | 9 h 30 min |
| February | 35°F | 14°F | 24.8°F | 1.83 | 7.9 | 8 | <1 | 27 | 10 h 30 min |
| March | 48°F | 26°F | 36.6°F | 2.51 | 3.6 | 9 | <1 | 24 | 11 h 50 min |
| April | 61°F | 36°F | 48.2°F | 3.90 | 0.8 | 11 | <1 | 11 | 13 h 20 min |
| May | 72°F | 47°F | 59.8°F | 4.57 | 0.0 | 13 | 1 | 2 | 14 h 30 min |
| June | 82°F | 57°F | 69.4°F | 5.49 | 0.0 | 12 | 5 | <1 | 15 h 10 min |
| July | 85°F | 60°F | 72.6°F | 4.89 | 0.0 | 9 | 7 | <1 | 15 h |
| August | 83°F | 58°F | 70.7°F | 3.91 | 0.0 | 9 | 4 | <1 | 14 h |
| September | 77°F | 50°F | 63.3°F | 3.71 | 0.0 | 9 | 2 | 1 | 12 h 30 min |
| October | 64°F | 38°F | 51.1°F | 3.02 | 0.4 | 9 | <1 | 10 | 11 h 10 min |
| November | 49°F | 27°F | 38.0°F | 2.60 | 1.7 | 8 | <1 | 21 | 9 h 50 min |
| December | 36°F | 17°F | 26.4°F | 2.21 | 8.8 | 9 | <1 | 29 | 9 h 10 min |
| Year (annual) | 60°F | 37°F | 48.5°F | 40.30 | 33.4 | 113 | 19 | 155 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −12°C | −6.2°C | 42 mm | 26 cm |
| February | 2°C | −10°C | −4.0°C | 46 mm | 20 cm |
| March | 9°C | −4°C | 2.6°C | 64 mm | 9 cm |
| April | 16°C | 2°C | 9.0°C | 99 mm | 2 cm |
| May | 22°C | 8°C | 15.4°C | 116 mm | 0 cm |
| June | 28°C | 14°C | 20.8°C | 139 mm | 0 cm |
| July | 29°C | 16°C | 22.6°C | 124 mm | 0 cm |
| August | 29°C | 15°C | 21.5°C | 99 mm | 0 cm |
| September | 25°C | 10°C | 17.4°C | 94 mm | 0 cm |
| October | 18°C | 3°C | 10.6°C | 77 mm | 1 cm |
| November | 9°C | −3°C | 3.3°C | 66 mm | 4 cm |
| December | 2°C | −8°C | −3.1°C | 56 mm | 22 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00115901; 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 Mount Carroll?
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 (9).
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 USC00115901.
When is the last frost in Mount Carroll?
In Mount Carroll, the last spring frost (32°F) comes after May 2 in half of years and after May 18 in one year in ten; the first autumn frost comes before October 7 in half of years and before September 24 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
- May 21 year in 10 after May 18; 9 in 10 after April 18
- First autumn frost, half of years before
- October 71 year in 10 before September 24; 9 in 10 before October 20
NOAA puts the median frost-free season at 154 days, and the season without a hard freeze (28°F) at 174 days.
A hard freeze (28°F) comes after April 23 in half of springs and before October 16 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Mount Carroll in zone 5a in ZIP code 61053, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Mount Carroll's NOAA station is in zone 5a: the coldest night of a typical year reaches −19°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 USC00115901; 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 Mount Carroll?
In a normal year in Mount Carroll, 19 days a year reach 90°F, 155 nights fall to 32°F or colder and 113 days bring measurable precipitation.
- Days at 90°F or more
- 19a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 155a normal year
- Days that stay below freezing
- 43high of 32°F or less
- Days with 0.01 inch of precipitation
- 113a normal year
- Days with 1 inch of snow or more
- 11a normal year
The highest temperature in this station's record (since 1897) is 108°F, on July 12, 1936; the lowest is −38°F, on January 31, 2019.
The wettest calendar year on that record is 2018, with 52.58 in; the snowiest season is 1978–79, with 77.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00115901; records: ACIS (NOAA Regional Climate Centers), station USC00115901. Records use complete months only; a month missing more than three days is left out.
How sunny is Mount Carroll?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Mount Carroll, 3.9 kWh per square metre a day. July is the sunniest month (80%) and December the cloudiest (61%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 66% | 1.8 |
| February | 70% | 2.8 |
| March | 69% | 3.8 |
| April | 68% | 4.7 |
| May | 71% | 5.5 |
| June | 76% | 6.2 |
| July | 80% | 6.3 |
| August | 79% | 5.5 |
| September | 78% | 4.4 |
| October | 70% | 2.9 |
| November | 67% | 1.9 |
| December | 61% | 1.4 |
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 Mount Carroll need?
A normal year in Mount Carroll brings 6,733 heating degree days, 25% more than the median U.S. place (5,373), and 746 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 2,917 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,370 | 0 |
| February | 1,126 | 0 |
| March | 882 | 1 |
| April | 509 | 5 |
| May | 211 | 50 |
| June | 35 | 165 |
| July | 7 | 244 |
| August | 16 | 192 |
| September | 130 | 77 |
| October | 441 | 10 |
| November | 812 | 0 |
| December | 1,195 | 0 |
| Year (annual) | 6,733 | 746 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00115901. 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 Mount Carroll been warmer than normal lately?
2024 averaged 51.6°F, 3.1°F above the 1991-2020 normal of 48.5°F. 3 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 49.6°F | +1.1°F | 34.11 | 27.6 |
| 2022 | 47.4°F | −1.1°F | 41.47 | 30.0 |
| 2023 | 50.2°F | +1.7°F | 32.63 | 38.1 |
| 2024 | 51.6°F | +3.1°F | 40.27 | 26.3 |
Over 93 complete years from 1889 to 2025, the station's annual mean temperature rose at a fitted 0.9°F per century (+0.05°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00115901; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Mount Carroll's climate compare?
Mount Carroll is warmer than 13 of the other 143 places with their own NOAA record in Illinois, and wetter than 76. Across the 7,247 U.S. stations with normals, its annual mean of 48.5°F is warmer than 34%.
In the Köppen classification computed from these normals, Mount Carroll 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 Mount Carroll 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.
- Savanna, IL2,713 people · 8 mi W
- Lanark, IL1,463 people · 8 mi E
- Lake Carroll, IL763 people · 8 mi NE
- Sabula, IA498 people · 10 mi W
- Chadwick, IL476 people · 8 mi SE
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 Mount Carroll's climate
What is the coldest month in Mount Carroll?
January, with a normal high of 31°F and a normal low of 11°F. The warmest is July (85°F by day, 60°F at night).
Does it snow in Mount Carroll?
Yes: 33 inches in a normal year, falling on 17 days with 0.1 inch or more, the most in January (10.2 inches).
What is the rainiest month in Mount Carroll?
June, with 5.49 in of precipitation in a normal year; the driest is January with 1.66 in.
What plant hardiness zone is Mount Carroll in?
The USDA's 2023 map puts Mount Carroll in zone 5a in ZIP code 61053, the nearest ZIP area. By the same method at Mount Carroll's NOAA station, the coldest night of a typical year reaches −19°F (28 years, 1991-2020): zone 5a.
How late can frost come in Mount Carroll?
In half of years the last 32°F night comes after May 2; in one year in ten it comes after May 18. Waiting until May 18 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Fulton, IL16 miles from this station, 49.9°F a year
- Elizabeth, IL19 miles from this station, 47.5°F a year
- Polo, IL20 miles from this station, 49.3°F a year
- Stockton, IL21 miles from this station, 47.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made