Smithland Lock and Dam, Illinois climate: Climate normals at a NOAA weather station
Smithland Lock and Dam's normal year runs from 26°F January nights to 88°F July afternoons, with 49.3 inches of precipitation and 4 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 13.9°C, January lows of −4°C, July highs of 31°C, 1,252 mm of precipitation a year.
- NOAA stationSmithland Lock and Dam
- Station IDUSC00118020
- Location37.16°N 88.43°W
- Elevation357 ft (109 m)
On October 23, the normal high in Smithland Lock and Dam is 67°F and the normal low 44°F, and the chance of measurable rain or snow is 25%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Smithland Lock and Dam.
- Jan 43° 26°
- Feb 47° 28°
- Mar 57° 37°
- Apr 68° 46°
- May 77° 56°
- Jun 85° 65°
- Jul 88° 69°
- Aug 87° 67°
- Sep 81° 60°
- Oct 70° 47°
- Nov 57° 37°
- Dec 46° 29°
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 Smithland Lock and Dam each month?
July is the warmest month, with normal highs of 88°F; January the coldest, with normal lows of 26°F. The most precipitation falls in April (5.07 in), the least in August (2.79 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 43°F | 26°F | 34.2°F | 3.71 | 0.4 | 10 | <1 | 23 | 9 h 50 min |
| February | 47°F | 28°F | 37.7°F | 4.10 | 1.2 | 9 | <1 | 18 | 10 h 50 min |
| March | 57°F | 37°F | 46.7°F | 4.78 | 0.4 | 11 | <1 | 11 | 11 h 50 min |
| April | 68°F | 46°F | 57.0°F | 5.07 | 0.0 | 11 | <1 | 2 | 13 h 10 min |
| May | 77°F | 56°F | 66.3°F | 4.56 | 0.0 | 11 | 1 | <1 | 14 h 10 min |
| June | 85°F | 65°F | 74.7°F | 4.30 | 0.0 | 9 | 7 | <1 | 14 h 40 min |
| July | 88°F | 69°F | 78.3°F | 4.26 | 0.0 | 8 | 13 | <1 | 14 h 30 min |
| August | 87°F | 67°F | 77.2°F | 2.79 | 0.0 | 7 | 11 | <1 | 13 h 40 min |
| September | 81°F | 60°F | 70.5°F | 3.57 | 0.0 | 7 | 5 | <1 | 12 h 30 min |
| October | 70°F | 47°F | 58.7°F | 3.61 | 0.0 | 7 | <1 | 2 | 11 h 20 min |
| November | 57°F | 37°F | 46.8°F | 4.19 | 0.0 | 9 | <1 | 11 | 10 h 10 min |
| December | 46°F | 29°F | 37.8°F | 4.35 | 1.8 | 10 | <1 | 20 | 9 h 40 min |
| Year (annual) | 67°F | 47°F | 57.1°F | 49.29 | 3.8 | 109 | 38 | 88 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 6°C | −4°C | 1.2°C | 94 mm | 1 cm |
| February | 8°C | −2°C | 3.2°C | 104 mm | 3 cm |
| March | 14°C | 3°C | 8.2°C | 121 mm | 1 cm |
| April | 20°C | 8°C | 13.9°C | 129 mm | 0 cm |
| May | 25°C | 13°C | 19.1°C | 116 mm | 0 cm |
| June | 29°C | 18°C | 23.7°C | 109 mm | 0 cm |
| July | 31°C | 20°C | 25.7°C | 108 mm | 0 cm |
| August | 31°C | 19°C | 25.1°C | 71 mm | 0 cm |
| September | 27°C | 15°C | 21.4°C | 91 mm | 0 cm |
| October | 21°C | 8°C | 14.8°C | 92 mm | 0 cm |
| November | 14°C | 3°C | 8.2°C | 106 mm | 0 cm |
| December | 8°C | −1°C | 3.2°C | 110 mm | 5 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00118020; 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 Smithland Lock and Dam?
Normal highs sit between 65°F and 85°F in April, May, June, 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 USC00118020.
When is the last frost at Smithland Lock and Dam?
In Smithland Lock and Dam, the last spring frost (32°F) comes after April 3 in half of years and after April 21 in one year in ten; the first autumn frost comes before October 30 in half of years and before October 17 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 31 year in 10 after April 21; 9 in 10 after March 18
- First autumn frost, half of years before
- October 301 year in 10 before October 17; 9 in 10 before November 12
NOAA puts the median frost-free season at 207 days, and the season without a hard freeze (28°F) at 230 days.
A hard freeze (28°F) comes after March 23 in half of springs and before November 8 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Smithland Lock and Dam in zone 7a in ZIP code 42081, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 7a: the coldest night of a typical year reaches 4°F (26 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 USC00118020; 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 at Smithland Lock and Dam?
In a normal year in Smithland Lock and Dam, 38 days a year reach 90°F (1 of them 100°F or more), 88 nights fall to 32°F or colder and 109 days bring measurable precipitation.
- Days at 90°F or more
- 38a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 88a normal year
- Days that stay below freezing
- 15high of 32°F or less
- Days with 0.01 inch of precipitation
- 109a normal year
- Days with 1 inch of snow or more
- 2a normal year
The highest temperature in this station's record (since 1981) is 106°F, on June 30, 2012; the lowest is −12°F, on December 23, 1989.
The wettest calendar year on that record is 2006, with 65.09 in; the snowiest season is 1993–94, with 15.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00118020; records: ACIS (NOAA Regional Climate Centers), station USC00118020. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Smithland Lock and Dam?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds at Smithland Lock and Dam, 4.2 kWh per square metre a day. August is the sunniest month (83%) and December the cloudiest (64%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 64% | 2.1 |
| February | 64% | 2.8 |
| March | 67% | 3.8 |
| April | 73% | 5.1 |
| May | 74% | 5.7 |
| June | 82% | 6.5 |
| July | 83% | 6.3 |
| August | 83% | 5.7 |
| September | 81% | 4.8 |
| October | 76% | 3.5 |
| November | 72% | 2.5 |
| December | 64% | 1.8 |
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 Smithland Lock and Dam record?
A normal year at Smithland Lock and Dam brings 4,297 heating degree days, 20% fewer than the median U.S. place (5,373), and 1,465 cooling degree days, 61% 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 4,329 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 953 | 0 |
| February | 766 | 0 |
| March | 573 | 4 |
| April | 265 | 27 |
| May | 77 | 118 |
| June | 5 | 294 |
| July | 0 | 411 |
| August | 1 | 377 |
| September | 30 | 193 |
| October | 235 | 38 |
| November | 550 | 3 |
| December | 842 | 0 |
| Year (annual) | 4,297 | 1,465 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00118020. 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 Smithland Lock and Dam been warmer than normal?
2025 averaged 58.6°F, 1.5°F above the 1991-2020 normal of 57.1°F. 2 of the 2 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 57.6°F | +0.5°F | 53.43 | – |
| 2025 | 58.6°F | +1.5°F | – | – |
Source: observed years: ACIS, station USC00118020. A year counts only with all twelve months complete.
How does Smithland Lock and Dam's climate compare?
Smithland Lock and Dam is warmer than 138 of the 144 places with their own NOAA record in Illinois, and wetter than 134. Across the 7,247 U.S. stations with normals, its annual mean of 57.1°F is warmer than 67%.
In the Köppen classification computed from these normals, Smithland Lock and Dam is Cfa: temperate, 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 Smithland Lock and Dam share this climate record?
8 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.
- Calvert City, KY2,517 people · 8 mi S
- Ledbetter, KY1,630 people · 9 mi SW
- Salem, KY706 people · 13 mi NE
- Gilbertsville, KY405 people · 12 mi SE
- Grand Rivers, KY345 people · 16 mi SE
- Smithland, KY237 people · 2 mi SE
- Crayne, KY106 people · 21 mi NE
- Burna, KY98 people · 7 mi NE
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 Smithland Lock and Dam's climate
What is the coldest month at Smithland Lock and Dam?
January, with a normal high of 43°F and a normal low of 26°F. The warmest is July (88°F by day, 69°F at night).
Does it snow at Smithland Lock and Dam?
Yes: 4 inches in a normal year, falling on 3 days with 0.1 inch or more, the most in December (1.8 inches).
What is the rainiest month at Smithland Lock and Dam?
April, with 5.07 in of precipitation in a normal year; the driest is August with 2.79 in.
What plant hardiness zone is Smithland Lock and Dam in?
The USDA's 2023 map puts Smithland Lock and Dam in zone 7a in ZIP code 42081, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches 4°F (26 years, 1991-2020): zone 7a.
How late can frost come at Smithland Lock and Dam?
In half of years the last 32°F night comes after April 3; in one year in ten it comes after April 21. Waiting until April 21 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Brookport, IL12 miles from this station, 57.3°F a year
- Paducah, KY20 miles from this station, 58.8°F a year
- Eddyville, KY21 miles from this station, 60.9°F a year
- Rosiclare, IL22 miles from this station, 54.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made