Hillsboro, Illinois climate: Normal weather by month, frost dates and records
Hillsboro's normal year runs from 21°F January nights to 89°F July afternoons, with 42.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 13.1°C, January lows of −6°C, July highs of 32°C, 1,069 mm of precipitation a year.
- NOAA stationHillsboro
- Station IDUSC00114108
- Location39.16°N 89.49°W
- Elevation630 ft (192 m)
- Population5,761
On October 23, the normal high in Hillsboro is 66°F and the normal low 44°F, and the chance of measurable rain or snow is 23%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Hillsboro.
- Jan 38° 21°
- Feb 45° 25°
- Mar 55° 34°
- Apr 68° 44°
- May 78° 54°
- Jun 86° 63°
- Jul 89° 67°
- Aug 87° 65°
- Sep 82° 57°
- Oct 70° 46°
- Nov 55° 35°
- Dec 43° 26°
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 Hillsboro each month?
July is the warmest month, with normal highs of 89°F; January the coldest, with normal lows of 21°F. The most precipitation falls in May (5.06 in), the least in January (2.52 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 38°F | 21°F | 29.9°F | 2.52 | 6 | <1 | 26 | 9 h 40 min |
| February | 45°F | 25°F | 34.9°F | 2.61 | 6 | <1 | 20 | 10 h 40 min |
| March | 55°F | 34°F | 44.8°F | 3.05 | 8 | <1 | 14 | 11 h 50 min |
| April | 68°F | 44°F | 56.2°F | 5.03 | 10 | <1 | 3 | 13 h 10 min |
| May | 78°F | 54°F | 66.0°F | 5.06 | 11 | 2 | <1 | 14 h 20 min |
| June | 86°F | 63°F | 74.6°F | 3.83 | 9 | 11 | <1 | 14 h 50 min |
| July | 89°F | 67°F | 77.6°F | 3.74 | 7 | 14 | <1 | 14 h 40 min |
| August | 87°F | 65°F | 76.0°F | 3.14 | 7 | 11 | <1 | 13 h 40 min |
| September | 82°F | 57°F | 69.2°F | 3.30 | 6 | 5 | <1 | 12 h 30 min |
| October | 70°F | 46°F | 57.8°F | 3.41 | 7 | <1 | 3 | 11 h 10 min |
| November | 55°F | 35°F | 44.9°F | 3.76 | 7 | <1 | 12 | 10 h |
| December | 43°F | 26°F | 34.6°F | 2.62 | 7 | <1 | 23 | 9 h 30 min |
| Year (annual) | 66°F | 45°F | 55.5°F | 42.07 | 91 | 42 | 100 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 4°C | −6°C | −1.2°C | 64 mm |
| February | 7°C | −4°C | 1.6°C | 66 mm |
| March | 13°C | 1°C | 7.1°C | 77 mm |
| April | 20°C | 7°C | 13.4°C | 128 mm |
| May | 25°C | 12°C | 18.9°C | 129 mm |
| June | 30°C | 17°C | 23.7°C | 97 mm |
| July | 32°C | 19°C | 25.3°C | 95 mm |
| August | 31°C | 18°C | 24.4°C | 80 mm |
| September | 28°C | 14°C | 20.7°C | 84 mm |
| October | 21°C | 8°C | 14.3°C | 87 mm |
| November | 13°C | 2°C | 7.2°C | 96 mm |
| December | 6°C | −3°C | 1.4°C | 67 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Morrisonville (18 miles away), gets 16 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114108; 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 Hillsboro?
Normal highs sit between 65°F and 85°F in April, May, September and October. Of those, September has the fewest days with rain (6).
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 USC00114108.
When is the last frost in Hillsboro?
In Hillsboro, the last spring frost (32°F) comes after April 13 in half of years and after April 28 in one year in ten; the first autumn frost comes before October 24 in half of years and before October 10 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 131 year in 10 after April 28; 9 in 10 after March 30
- First autumn frost, half of years before
- October 241 year in 10 before October 10; 9 in 10 before November 4
NOAA puts the median frost-free season at 192 days, and the season without a hard freeze (28°F) at 214 days.
A hard freeze (28°F) comes after April 2 in half of springs and before November 2 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Hillsboro in zone 6b in ZIP code 62049, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Hillsboro's NOAA station is in zone 6b: the coldest night of a typical year reaches −4°F (24 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 USC00114108; 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 Hillsboro?
In a normal year in Hillsboro, 42 days a year reach 90°F (2 of them 100°F or more), 100 nights fall to 32°F or colder and 91 days bring measurable precipitation.
- Days at 90°F or more
- 42a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 100a normal year
- Days that stay below freezing
- 23high of 32°F or less
- Days with 0.01 inch of precipitation
- 91a normal year
The highest temperature in this station's record (since 1895) is 114°F, on July 14, 1954; the lowest is −22°F, on February 14, 1905.
The wettest calendar year on that record is 1973, with 56.65 in; the snowiest season is 1911–12, with 58.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00114108; records: ACIS (NOAA Regional Climate Centers), station USC00114108. Records use complete months only; a month missing more than three days is left out.
How sunny is Hillsboro?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Hillsboro, 4.1 kWh per square metre a day. July is the sunniest month (83%) and December the cloudiest (63%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 64% | 1.9 |
| February | 66% | 2.8 |
| March | 67% | 3.7 |
| April | 72% | 5.0 |
| May | 73% | 5.6 |
| June | 81% | 6.4 |
| July | 83% | 6.4 |
| August | 82% | 5.7 |
| September | 82% | 4.7 |
| October | 74% | 3.3 |
| November | 71% | 2.3 |
| December | 63% | 1.6 |
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 Hillsboro need?
A normal year in Hillsboro brings 4,799 heating degree days, 11% fewer than the median U.S. place (5,373), and 1,389 cooling degree days, 53% 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 4,156 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,088 | 0 |
| February | 842 | 0 |
| March | 631 | 5 |
| April | 291 | 26 |
| May | 89 | 120 |
| June | 7 | 296 |
| July | 1 | 393 |
| August | 1 | 342 |
| September | 43 | 169 |
| October | 261 | 36 |
| November | 605 | 2 |
| December | 942 | 0 |
| Year (annual) | 4,799 | 1,389 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114108. 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 Hillsboro been warmer than normal lately?
Over 80 complete years from 1897 to 2025, the station's annual mean temperature rose at a fitted 0.4°F per century (+0.02°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Hillsboro's climate compare?
Hillsboro is warmer than 126 of the other 143 places with their own NOAA record in Illinois, and wetter than 102. Across the 7,247 U.S. stations with normals, its annual mean of 55.5°F is warmer than 62%.
In the Köppen classification computed from these normals, Hillsboro 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 Hillsboro share this climate record?
18 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.
- Litchfield, IL6,587 people · 9 mi W
- Staunton, IL4,935 people · 19 mi SW
- Mount Olive, IL1,941 people · 14 mi SW
- Witt, IL766 people · 10 mi NE
- Livingston, IL749 people · 20 mi SW
- Taylor Springs, IL725 people · 2 mi S
- Coffeen, IL628 people · 7 mi SE
- Schram City, IL554 people · 1 mi E
- Sorento, IL409 people · 12 mi S
- Irving, IL363 people · 6 mi NE
- New Douglas, IL339 people · 16 mi SW
- Panama, IL321 people · 9 mi S
- Lake Ka-Ho, IL198 people · 14 mi W
- Williamson, IL174 people · 19 mi SW
- Butler, IL163 people · 3 mi NW
- Donnellson, IL150 people · 9 mi S
- Old Ripley, IL80 people · 19 mi S
- Walshville, IL60 people · 9 mi SW
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 Hillsboro's climate
What is the coldest month in Hillsboro?
January, with a normal high of 38°F and a normal low of 21°F. The warmest is July (89°F by day, 67°F at night).
Does it snow in Hillsboro?
Yes. NOAA publishes no 1991-2020 snowfall normal for Hillsboro's NOAA station; the nearest record that keeps one, Morrisonville (18 miles away), records 16 inches of snow in a normal year.
What is the rainiest month in Hillsboro?
May, with 5.06 in of precipitation in a normal year; the driest is January with 2.52 in.
What plant hardiness zone is Hillsboro in?
The USDA's 2023 map puts Hillsboro in zone 6b in ZIP code 62049, the nearest ZIP area. By the same method at Hillsboro's NOAA station, the coldest night of a typical year reaches −4°F (24 years, 1991-2020): zone 6b.
How late can frost come in Hillsboro?
In half of years the last 32°F night comes after April 13; in one year in ten it comes after April 28. Waiting until April 28 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Morrisonville, IL17 miles from this station, 53.6°F a year
- Ramsey, IL21 miles from this station, 52.5°F a year
- Carlinville, IL22 miles from this station, 53.4°F a year
- Vandalia, IL25 miles from this station, 54.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made