Rock Island, Illinois climate: Normal weather by month, frost dates and records
Rock Island's normal year runs from 13°F January nights to 84°F July afternoons, with 38.8 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.2°C, January lows of −10°C, July highs of 29°C, 986 mm of precipitation a year.
- NOAA stationRock Island Lock and Dam 15
- Station IDUSC00117391
- Location41.52°N 90.56°W
- Elevation568 ft (173 m)
- From the center4 miles
- Population36,434
On October 14, the normal high in Rock Island is 65°F and the normal low 44°F, and the chance of measurable rain or snow is 30%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Rock Island.
- Jan 31° 13°
- Feb 36° 18°
- Mar 48° 28°
- Apr 61° 39°
- May 72° 51°
- Jun 81° 61°
- Jul 84° 65°
- Aug 82° 63°
- Sep 77° 55°
- Oct 64° 43°
- Nov 49° 30°
- Dec 36° 20°
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 Rock Island each month?
July is the warmest month, with normal highs of 84°F; January the coldest, with normal lows of 13°F. The most precipitation falls in June (5.22 in), the least in January (1.49 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 31°F | 13°F | 22.2°F | 1.49 | 11 | <1 | 29 | 9 h 30 min |
| February | 36°F | 18°F | 27.1°F | 1.78 | 9 | <1 | 25 | 10 h 40 min |
| March | 48°F | 28°F | 38.2°F | 2.62 | 10 | <1 | 18 | 11 h 50 min |
| April | 61°F | 39°F | 50.3°F | 3.81 | 12 | <1 | 4 | 13 h 20 min |
| May | 72°F | 51°F | 61.6°F | 5.12 | 13 | 1 | <1 | 14 h 30 min |
| June | 81°F | 61°F | 71.1°F | 5.22 | 12 | 4 | <1 | 15 h 10 min |
| July | 84°F | 65°F | 74.4°F | 4.22 | 9 | 7 | <1 | 14 h 50 min |
| August | 82°F | 63°F | 72.7°F | 4.03 | 10 | 4 | <1 | 13 h 50 min |
| September | 77°F | 55°F | 65.8°F | 3.31 | 8 | 2 | <1 | 12 h 30 min |
| October | 64°F | 43°F | 53.3°F | 2.89 | 10 | <1 | 2 | 11 h 10 min |
| November | 49°F | 30°F | 39.4°F | 2.30 | 10 | <1 | 14 | 9 h 50 min |
| December | 36°F | 20°F | 27.8°F | 2.02 | 10 | <1 | 26 | 9 h 10 min |
| Year (annual) | 60°F | 41°F | 50.3°F | 38.81 | 123 | 18 | 118 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −10°C | −5.4°C | 38 mm |
| February | 2°C | −8°C | −2.7°C | 45 mm |
| March | 9°C | −2°C | 3.4°C | 67 mm |
| April | 16°C | 4°C | 10.2°C | 97 mm |
| May | 22°C | 10°C | 16.4°C | 130 mm |
| June | 27°C | 16°C | 21.7°C | 133 mm |
| July | 29°C | 18°C | 23.6°C | 107 mm |
| August | 28°C | 17°C | 22.6°C | 102 mm |
| September | 25°C | 13°C | 18.8°C | 84 mm |
| October | 18°C | 6°C | 11.8°C | 73 mm |
| November | 9°C | −1°C | 4.1°C | 58 mm |
| December | 2°C | −7°C | −2.3°C | 51 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Moline (4 miles away), gets 36 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00117391; 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 Rock Island?
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 (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 USC00117391.
When is the last frost in Rock Island?
In Rock Island, the last spring frost (32°F) comes after April 19 in half of years and after May 4 in one year in ten; the first autumn frost comes before October 22 in half of years and before October 7 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 191 year in 10 after May 4; 9 in 10 after April 6
- First autumn frost, half of years before
- October 221 year in 10 before October 7; 9 in 10 before November 2
NOAA puts the median frost-free season at 184 days, and the season without a hard freeze (28°F) at 204 days.
A hard freeze (28°F) comes after April 8 in half of springs and before October 31 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Rock Island in zone 5b in ZIP code 61201. By the map's own method, the average of each year's coldest night over 1991-2020, Rock Island's NOAA station is in zone 6a: the coldest night of a typical year reaches −8°F (23 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 USC00117391; 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 Rock Island?
In a normal year in Rock Island, 18 days a year reach 90°F, 118 nights fall to 32°F or colder and 123 days bring measurable precipitation.
- Days at 90°F or more
- 18a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 118a normal year
- Days that stay below freezing
- 42high of 32°F or less
- Days with 0.01 inch of precipitation
- 123a normal year
The highest temperature in this station's record (since 1985) is 103°F, on July 17, 2006; the lowest is −32°F, on January 31, 2019.
The wettest calendar year on that record is 1990, with 49.07 in; the snowiest season is 1950–51, with 47.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00117391; records: ACIS (NOAA Regional Climate Centers), station USC00117391. Records use complete months only; a month missing more than three days is left out.
How sunny is Rock Island?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Rock Island, 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 Rock Island need?
A normal year in Rock Island brings 6,241 heating degree days, 16% more than the median U.S. place (5,373), and 935 cooling degree days, 3% 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 3,293 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,327 | 0 |
| February | 1,061 | 0 |
| March | 832 | 1 |
| April | 447 | 7 |
| May | 169 | 62 |
| June | 20 | 203 |
| July | 2 | 293 |
| August | 6 | 246 |
| September | 83 | 108 |
| October | 377 | 15 |
| November | 767 | 0 |
| December | 1,152 | 0 |
| Year (annual) | 6,241 | 935 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00117391. 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 Rock Island been warmer than normal lately?
2022 averaged 51.1°F, 0.8°F above the 1991-2020 normal of 50.3°F. 2 of the 2 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 53.3°F | +3.0°F | 32.44 |
| 2022 | 51.1°F | +0.8°F | 31.72 |
Source: observed years: ACIS, station USC00117391. A year counts only with all twelve months complete.
How does Rock Island's climate compare?
Rock Island is warmer than 41 of the other 143 places with their own NOAA record in Illinois, and wetter than 49. Across the 7,247 U.S. stations with normals, its annual mean of 50.3°F is warmer than 42%.
In the Köppen classification computed from these normals, Rock Island 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 Rock Island share this climate record?
17 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.
- Bettendorf, IA40,281 people · 6 mi NE
- Eldridge, IA6,967 people · 8 mi N
- Park View, IA2,861 people · 12 mi N
- Blue Grass, IA1,707 people · 11 mi W
- Walcott, IA1,556 people · 12 mi NW
- Buffalo, IA1,163 people · 11 mi W
- Princeton, IA917 people · 15 mi NE
- Long Grove, IA849 people · 12 mi N
- Grand Mound, IA608 people · 22 mi N
- Riverdale, IA385 people · 5 mi E
- Donahue, IA336 people · 13 mi NW
- McCausland, IA314 people · 17 mi N
- Dixon, IA204 people · 19 mi NW
- Maysville, IA155 people · 12 mi NW
- Panorama Park, IA142 people · 6 mi NE
- Argo, IA11 people · 10 mi NE
- Plainview, IA10 people · 15 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 Rock Island's climate
What is the coldest month in Rock Island?
January, with a normal high of 31°F and a normal low of 13°F. The warmest is July (84°F by day, 65°F at night).
Does it snow in Rock Island?
Yes. NOAA publishes no 1991-2020 snowfall normal for Rock Island's NOAA station; the nearest record that keeps one, Moline (4 miles away), records 36 inches of snow in a normal year.
What is the rainiest month in Rock Island?
June, with 5.22 in of precipitation in a normal year; the driest is January with 1.49 in.
What plant hardiness zone is Rock Island in?
The USDA's 2023 map puts Rock Island in zone 5b in ZIP code 61201. By the same method at Rock Island's NOAA station, the coldest night of a typical year reaches −8°F (23 years, 1991-2020): zone 6a.
How late can frost come in Rock Island?
In half of years the last 32°F night comes after April 19; in one year in ten it comes after May 4. Waiting until May 4 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Moline, IL4 miles from this station, 51.2°F a year
- Davenport, IA6 miles from this station, 49.9°F a year
- Le Claire, IA9 miles from this station, 50.6°F a year
- Geneseo, IL22 miles from this station, 50.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made