Lacon, Illinois climate: Normal weather by month, frost dates and records
Lacon's normal year runs from 18°F January nights to 87°F July afternoons, with 38.4 inches of precipitation and 25 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 11.4°C, January lows of −8°C, July highs of 31°C, 975 mm of precipitation a year.
- NOAA stationLacon
- Station IDUSC00114805
- Location41.02°N 89.42°W
- Elevation458 ft (140 m)
- Population1,838
On October 23, the normal high in Lacon is 63°F and the normal low 41°F, and the chance of measurable rain or snow is 31%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Lacon.
- Jan 34° 18°
- Feb 38° 22°
- Mar 51° 31°
- Apr 65° 41°
- May 75° 52°
- Jun 84° 61°
- Jul 87° 65°
- Aug 86° 63°
- Sep 80° 55°
- Oct 67° 44°
- Nov 51° 33°
- Dec 38° 23°
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 Lacon each month?
July is the warmest month, with normal highs of 87°F; January the coldest, with normal lows of 18°F. The most precipitation falls in May (4.76 in), the least in February (2.06 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 34°F | 18°F | 25.9°F | 2.07 | 8.1 | 9 | <1 | 27 | 9 h 30 min |
| February | 38°F | 22°F | 29.9°F | 2.06 | 6.2 | 8 | <1 | 23 | 10 h 40 min |
| March | 51°F | 31°F | 41.4°F | 2.65 | 3.2 | 10 | <1 | 19 | 11 h 50 min |
| April | 65°F | 41°F | 52.9°F | 4.00 | 0.7 | 11 | <1 | 6 | 13 h 20 min |
| May | 75°F | 52°F | 63.3°F | 4.76 | 0.0 | 12 | 1 | <1 | 14 h 30 min |
| June | 84°F | 61°F | 72.8°F | 4.29 | 0.0 | 10 | 7 | <1 | 15 h 10 min |
| July | 87°F | 65°F | 76.0°F | 3.97 | 0.0 | 9 | 10 | <1 | 14 h 50 min |
| August | 86°F | 63°F | 74.3°F | 3.33 | 0.0 | 9 | 8 | <1 | 13 h 50 min |
| September | 80°F | 55°F | 67.4°F | 3.30 | 0.0 | 8 | 3 | <1 | 12 h 30 min |
| October | 67°F | 44°F | 55.0°F | 3.16 | 0.1 | 10 | <1 | 4 | 11 h 10 min |
| November | 51°F | 33°F | 41.9°F | 2.63 | 1.1 | 9 | <1 | 16 | 10 h |
| December | 38°F | 23°F | 30.8°F | 2.17 | 5.2 | 9 | <1 | 26 | 9 h 20 min |
| Year (annual) | 63°F | 42°F | 52.6°F | 38.39 | 24.6 | 114 | 29 | 121 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 1°C | −8°C | −3.4°C | 53 mm | 21 cm |
| February | 3°C | −6°C | −1.2°C | 52 mm | 16 cm |
| March | 11°C | 0°C | 5.2°C | 67 mm | 8 cm |
| April | 18°C | 5°C | 11.6°C | 102 mm | 2 cm |
| May | 24°C | 11°C | 17.4°C | 121 mm | 0 cm |
| June | 29°C | 16°C | 22.7°C | 109 mm | 0 cm |
| July | 31°C | 18°C | 24.4°C | 101 mm | 0 cm |
| August | 30°C | 17°C | 23.5°C | 85 mm | 0 cm |
| September | 26°C | 13°C | 19.7°C | 84 mm | 0 cm |
| October | 19°C | 6°C | 12.8°C | 80 mm | 0 cm |
| November | 11°C | 0°C | 5.5°C | 67 mm | 3 cm |
| December | 3°C | −5°C | −0.7°C | 55 mm | 13 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114805; 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 Lacon?
Normal highs sit between 65°F and 85°F in May, June, September and October. 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 USC00114805.
When is the last frost in Lacon?
In Lacon, the last spring frost (32°F) comes after April 20 in half of years and after May 7 in one year in ten; the first autumn frost comes before October 17 in half of years and before October 3 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 201 year in 10 after May 7; 9 in 10 after April 5
- First autumn frost, half of years before
- October 171 year in 10 before October 3; 9 in 10 before November 1
NOAA puts the median frost-free season at 178 days, and the season without a hard freeze (28°F) at 203 days.
A hard freeze (28°F) comes after April 7 in half of springs and before October 28 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Lacon in zone 5b in ZIP code 61540, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Lacon's NOAA station is in zone 6a: the coldest night of a typical year reaches −10°F (18 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 USC00114805; 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 Lacon?
In a normal year in Lacon, 29 days a year reach 90°F, 121 nights fall to 32°F or colder and 114 days bring measurable precipitation.
- Days at 90°F or more
- 29a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 121a normal year
- Days that stay below freezing
- 34high of 32°F or less
- Days with 0.01 inch of precipitation
- 114a normal year
- Days with 1 inch of snow or more
- 8a normal year
The highest temperature in this station's record (since 1950) is 103°F, on July 14, 1977; the lowest is −27°F, on January 5, 1999.
The wettest calendar year on that record is 1970, with 56.99 in; the snowiest season is 1959–60, with 44.2 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00114805; records: ACIS (NOAA Regional Climate Centers), station USC00114805. Records use complete months only; a month missing more than three days is left out.
How sunny is Lacon?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Lacon, 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 | 68% | 2.7 |
| March | 68% | 3.7 |
| April | 70% | 4.8 |
| May | 72% | 5.5 |
| June | 77% | 6.2 |
| July | 81% | 6.3 |
| August | 80% | 5.5 |
| September | 80% | 4.5 |
| October | 72% | 3.0 |
| November | 68% | 2.0 |
| 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 Lacon need?
A normal year in Lacon brings 5,603 heating degree days, 4% more than the median U.S. place (5,373), and 1,134 cooling degree days, 25% 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 3,652 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,212 | 0 |
| February | 983 | 0 |
| March | 734 | 1 |
| April | 376 | 15 |
| May | 131 | 79 |
| June | 13 | 247 |
| July | 0 | 343 |
| August | 4 | 292 |
| September | 65 | 135 |
| October | 331 | 22 |
| November | 693 | 0 |
| December | 1,062 | 0 |
| Year (annual) | 5,603 | 1,134 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114805. 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.
How does Lacon's climate compare?
Lacon is warmer than 87 of the other 143 places with their own NOAA record in Illinois, and wetter than 40. Across the 7,247 U.S. stations with normals, its annual mean of 52.6°F is warmer than 52%.
In the Köppen classification computed from these normals, Lacon 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 Lacon 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.
- Chillicothe, IL6,052 people · 8 mi SW
- Henry, IL2,298 people · 7 mi NE
- Rome, IL1,628 people · 11 mi SW
- Washburn, IL1,011 people · 9 mi SE
- Hopewell, IL415 people · 3 mi SW
- Varna, IL372 people · 10 mi E
- Sparland, IL355 people · 2 mi NW
- Lowpoint, IL184 people · 11 mi SE
- La Rose, IL98 people · 10 mi E
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 Lacon's climate
What is the coldest month in Lacon?
January, with a normal high of 34°F and a normal low of 18°F. The warmest is July (87°F by day, 65°F at night).
Does it snow in Lacon?
Yes: 25 inches in a normal year, falling on 19 days with 0.1 inch or more, the most in January (8.1 inches).
What is the rainiest month in Lacon?
May, with 4.76 in of precipitation in a normal year; the driest is February with 2.06 in.
What plant hardiness zone is Lacon in?
The USDA's 2023 map puts Lacon in zone 5b in ZIP code 61540, the nearest ZIP area. By the same method at Lacon's NOAA station, the coldest night of a typical year reaches −10°F (18 years, 1991-2020): zone 6a.
How late can frost come in Lacon?
In half of years the last 32°F night comes after April 20; in one year in ten it comes after May 7. Waiting until May 7 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Hennepin, IL17 miles from this station, 51.4°F a year
- Princeville, IL19 miles from this station, 50.8°F a year
- Minonk, IL21 miles from this station, 51.3°F a year
- Princeton, IL24 miles from this station, 49.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made