Rend Lake Dam, Illinois climate: Climate normals at a NOAA weather station
Rend Lake Dam's normal year runs from 22°F January nights to 88°F July afternoons, with 46.0 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 13.3°C, January lows of −6°C, July highs of 31°C, 1,168 mm of precipitation a year.
- NOAA stationRend Lake Dam
- Station IDUSC00117187
- Location38.04°N 88.99°W
- Elevation455 ft (139 m)
On October 23, the normal high in Rend Lake Dam is 66°F and the normal low 43°F, and the chance of measurable rain or snow is 27%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Rend Lake Dam.
- Jan 40° 22°
- Feb 44° 25°
- Mar 55° 35°
- Apr 68° 45°
- May 76° 56°
- Jun 86° 65°
- Jul 88° 68°
- Aug 87° 66°
- Sep 81° 58°
- Oct 69° 46°
- Nov 55° 35°
- Dec 44° 27°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like at Rend Lake Dam each month?
July is the warmest month, with normal highs of 88°F; January the coldest, with normal lows of 22°F. The most precipitation falls in April (5.43 in), the least in February (2.80 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 40°F | 22°F | 30.7°F | 3.18 | 8 | <1 | 26 | 9 h 50 min |
| February | 44°F | 25°F | 34.2°F | 2.80 | 8 | <1 | 21 | 10 h 50 min |
| March | 55°F | 35°F | 45.0°F | 4.21 | 10 | <1 | 11 | 11 h 50 min |
| April | 68°F | 45°F | 56.6°F | 5.43 | 11 | <1 | 2 | 13 h 10 min |
| May | 76°F | 56°F | 66.2°F | 5.07 | 13 | 1 | <1 | 14 h 10 min |
| June | 86°F | 65°F | 75.5°F | 4.48 | 9 | 9 | <1 | 14 h 50 min |
| July | 88°F | 68°F | 78.3°F | 3.96 | 8 | 12 | <1 | 14 h 30 min |
| August | 87°F | 66°F | 76.7°F | 3.35 | 7 | 8 | <1 | 13 h 40 min |
| September | 81°F | 58°F | 69.2°F | 3.22 | 7 | 5 | <1 | 12 h 30 min |
| October | 69°F | 46°F | 57.7°F | 3.44 | 8 | <1 | 2 | 11 h 20 min |
| November | 55°F | 35°F | 45.4°F | 3.97 | 8 | <1 | 14 | 10 h 10 min |
| December | 44°F | 27°F | 35.4°F | 2.89 | 8 | <1 | 24 | 9 h 30 min |
| Year (annual) | 66°F | 46°F | 55.9°F | 46.00 | 105 | 35 | 100 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 4°C | −6°C | −0.7°C | 81 mm |
| February | 7°C | −4°C | 1.2°C | 71 mm |
| March | 13°C | 1°C | 7.2°C | 107 mm |
| April | 20°C | 7°C | 13.7°C | 138 mm |
| May | 25°C | 13°C | 19.0°C | 129 mm |
| June | 30°C | 18°C | 24.2°C | 114 mm |
| July | 31°C | 20°C | 25.7°C | 101 mm |
| August | 31°C | 19°C | 24.8°C | 85 mm |
| September | 27°C | 14°C | 20.7°C | 82 mm |
| October | 21°C | 8°C | 14.3°C | 87 mm |
| November | 13°C | 2°C | 7.4°C | 101 mm |
| December | 7°C | −3°C | 1.9°C | 73 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Du Quoin (12 miles away), gets 12 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00117187; 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.
Which months are mildest at Rend Lake Dam?
Normal highs sit between 65°F and 85°F in April, May, September and October. 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 USC00117187.
When is the last frost at Rend Lake Dam?
In Rend Lake Dam, the last spring frost (32°F) comes after April 4 in half of years and after April 19 in one year in ten; the first autumn frost comes before October 27 in half of years and before October 16 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 41 year in 10 after April 19; 9 in 10 after March 21
- First autumn frost, half of years before
- October 271 year in 10 before October 16; 9 in 10 before November 8
NOAA puts the median frost-free season at 204 days, and the season without a hard freeze (28°F) at 223 days.
A hard freeze (28°F) comes after March 26 in half of springs and before November 5 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Rend Lake Dam in zone 7a in ZIP code 62891, 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 USC00117187; 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 at Rend Lake Dam?
In a normal year in Rend Lake Dam, 35 days a year reach 90°F, 100 nights fall to 32°F or colder and 105 days bring measurable precipitation.
- Days at 90°F or more
- 35a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 100a normal year
- Days that stay below freezing
- 25high of 32°F or less
- Days with 0.01 inch of precipitation
- 105a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00117187.
How sunny is it at Rend Lake Dam?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds at Rend Lake Dam, 4.2 kWh per square metre a day. August is the sunniest month (83%) and December the cloudiest (63%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 65% | 2.0 |
| February | 66% | 2.8 |
| March | 67% | 3.7 |
| April | 73% | 5.0 |
| May | 73% | 5.6 |
| June | 82% | 6.5 |
| July | 83% | 6.3 |
| August | 83% | 5.7 |
| September | 81% | 4.7 |
| October | 76% | 3.4 |
| November | 71% | 2.4 |
| December | 63% | 1.7 |
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 many heating and cooling degree days does Rend Lake Dam record?
A normal year at Rend Lake Dam brings 4,734 heating degree days, 12% fewer than the median U.S. place (5,373), and 1,449 cooling degree days, 60% more than the median (908). Five months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 4,193 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,063 | 0 |
| February | 862 | 0 |
| March | 622 | 2 |
| April | 274 | 21 |
| May | 91 | 128 |
| June | 3 | 316 |
| July | 0 | 411 |
| August | 1 | 362 |
| September | 42 | 168 |
| October | 266 | 40 |
| November | 592 | 3 |
| December | 919 | 0 |
| Year (annual) | 4,734 | 1,449 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00117187. 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.
Have recent years at Rend Lake Dam been warmer than normal?
2021 averaged 57.0°F, 1.1°F above the 1991-2020 normal of 55.9°F.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 57.0°F | +1.1°F | – |
Source: observed years: ACIS, station USC00117187. A year counts only with all twelve months complete.
How does Rend Lake Dam's climate compare?
Rend Lake Dam is warmer than 130 of the 144 places with their own NOAA record in Illinois, and wetter than 123. Across the 7,247 U.S. stations with normals, its annual mean of 55.9°F is warmer than 63%.
In the Köppen classification computed from these normals, Rend Lake Dam 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 Rend Lake Dam share this climate record?
9 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.
- Christopher, IL2,621 people · 6 mi SW
- Sesser, IL1,876 people · 5 mi NW
- Valier, IL539 people · 3 mi SW
- North City, IL499 people · 5 mi SW
- Waltonville, IL402 people · 12 mi N
- Buckner, IL398 people · 4 mi S
- Orient, IL321 people · 9 mi S
- Freeman Spur, IL271 people · 12 mi S
- Nason, IL196 people · 9 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 Rend Lake Dam's climate
What is the coldest month at Rend Lake Dam?
January, with a normal high of 40°F and a normal low of 22°F. The warmest is July (88°F by day, 68°F at night).
Does it snow at Rend Lake Dam?
Yes. NOAA publishes no 1991-2020 snowfall normal for the station; the nearest record that keeps one, Du Quoin (12 miles away), records 12 inches of snow in a normal year.
What is the rainiest month at Rend Lake Dam?
April, with 5.43 in of precipitation in a normal year; the driest is February with 2.80 in.
What plant hardiness zone is Rend Lake Dam in?
The USDA's 2023 map puts Rend Lake Dam in zone 7a in ZIP code 62891, the nearest ZIP area.
How late can frost come at Rend Lake Dam?
In half of years the last 32°F night comes after April 4; in one year in ten it comes after April 19. Waiting until April 19 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Benton, IL4 miles from this station, 56.3°F a year
- Du Quoin, IL12 miles from this station, 56.0°F a year
- Mount Vernon, IL22 miles from this station, 54.5°F a year
- Carbondale, IL23 miles from this station, 56.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made