Climate Comfort Score
78/100
Good
NOAA 1991–2020 normals 57°F annual avg Public-domain federal data
Harrisburg, IL Climate
Annual temperature, rainfall, and a comfort score, sourced from NOAA NCEI's 1991–2020 normals →
- 57°F
- Avg annual temp
- 78/100
- Comfort score
- 47.6"
- Annual precip
- 202d
- Growing season
30-year climate normals from 1 weather station (1991-2020).
The climate verdict for Harrisburg
Harrisburg, Illinois averages 57°F a year and scores 78/100 on the comfort index - good, milder than 74% of U.S. cities.
- 57°F
- yearly average temperature, NOAA normal
- 78/100
- comfort score, milder than 74% of U.S. cities
- 47.6"
- yearly precipitation total
- 202 days
- frost-free growing season
Based on NOAA U.S. Climate Normals (1991–2020) - 30-year averages describing the typical year, not a forecast.
Avg Temperature
57°F (14°C)
Avg High
68°F
Avg Low
47°F
Annual Precip
47.6"
Comfort Score
78/100
Good
Avg Annual Temperature
57°F
30-year mean (NOAA NCEI)
Annual Precipitation
47.6"
Liquid-equivalent total
Comfort score vs national 100-point ceiling (Harrisburg) 78.0%
National median (63)
PlainClimate composite, temperature mildness, humidity, precipitation, extreme-weather frequency. Good for the Harrisburg area.
How Harrisburg compares to every U.S. city
Harrisburg's comfort score vs. all U.S. cities
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
78 Top 26% higher than 74% of 6,915 US cities
Each bar is a band; taller bars hold more US cities. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Warming context for Harrisburg
MethodologySince 1900, U.S. land temperatures have tracked (and diverged from) the global mean - the chart below shows how. Harrisburg's current NOAA 1991-2020 normal sits within that longer spread, and the most recent decade runs warmer than the 30-year mean.
- United States land mean (NOAA NCEI) +0.11 °C/decade
- Global anomaly (NASA GISTEMP) +0.11 °C/decade
- Paris Agreement thresholds 1.5°C / 2.0°C
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|
| January | 43°F (6°C) | 24°F (-4°C) | 33°F (1°C) | 3.8" | 24.5 | 0.0 |
| February | 48°F (9°C) | 28°F (-2°C) | 38°F (3°C) | 3.1" | 19.8 | 0.0 |
| March | 58°F (15°C) | 36°F (2°C) | 47°F (8°C) | 4.9" | 12.6 | 0.0 |
| April | 69°F (21°C) | 46°F (8°C) | 58°F (14°C) | 5.3" | 2.6 | 0.4 |
| May | 78°F (26°C) | 57°F (14°C) | 67°F (20°C) | 4.3" | 0.0 | 1.1 |
| June | 86°F (30°C) | 65°F (18°C) | 76°F (24°C) | 4.9" | 0.0 | 9.2 |
| July | 89°F (32°C) | 68°F (20°C) | 79°F (26°C) | 3.5" | 0.0 | 14.1 |
| August | 88°F (31°C) | 66°F (19°C) | 77°F (25°C) | 3.6" | 0.0 | 13.1 |
| September | 82°F (28°C) | 57°F (14°C) | 70°F (21°C) | 3.1" | 0.1 | 5.1 |
| October | 71°F (22°C) | 45°F (7°C) | 58°F (15°C) | 3.8" | 2.5 | 0.3 |
| November | 57°F (14°C) | 36°F (2°C) | 47°F (8°C) | 4.0" | 11.7 | 0.0 |
| December | 47°F (8°C) | 29°F (-2°C) | 38°F (3°C) | 3.4" | 21.1 | 0.0 |
Monthly Precipitation
Average monthly rainfall
January 3.8"
7.8 days with precipitation
February 3.1"
6.3 days with precipitation
March 4.9"
8.9 days with precipitation
April 5.3"
10.9 days with precipitation
May 4.3"
9.4 days with precipitation
June 4.9"
7.9 days with precipitation
July 3.5"
6.9 days with precipitation
August 3.6"
6.0 days with precipitation
September 3.1"
6.3 days with precipitation
October 3.8"
6.2 days with precipitation
November 4.0"
7.6 days with precipitation
December 3.4"
8.1 days with precipitation
Frost Dates & Growing Season
First Fall Freeze
October 26
50% probability date
Last Spring Freeze
April 7
50% probability date
Growing Season
202 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
4,299
Higher = more heating needed
Cooling Degree Days
1,522
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
What Harrisburg's climate means for you
Harrisburg runs 57°F a year - peaking in July, coldest in January.
- Gardeners get about 202 frost-free days, with the last spring freeze near April 7 - plan the planting calendar around it, not the regional average.
- Energy bills track 4,299 heating and 1,522 cooling degree days a year, higher means the furnace or AC runs more.
- Comparing places to live? Line this city up against nearby cities and the national rankings. See rankings
These are 30-year NOAA normals (1991–2020) - the typical year, not a forecast for any specific season.
Climate Guides
Climate Insight: Harrisburg, IL
Harrisburg, Illinois runs an annual average of 57°F, ranging from a mean daily high of 68°F to a mean daily low of 47°F, per NOAA's 1991–2020 climate normals. July is typically the warmest month of the year, while January is the coldest. Drawn from station USC00113879, these thirty-year averages smooth out year-to-year swings into a baseline for what a typical month looks like here.
Precipitation patterns matter as much as temperature for anyone planning to live, garden, or travel here. Harrisburg receives roughly 47.6 inches of precipitation each year, predominantly as rainfall. The frost-free season averages 202 days, which directly shapes the planting calendar and growing potential for the area, with the last spring freeze near April 7 and the first fall freeze near October 26. For energy use, 4,299 heating degree days and 1,522 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.
On PlainClimate's composite comfort index, Harrisburg scores 78/100 (Good), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. Use the monthly tables above to plan around specific windows, shoulder seasons for mild highs and lows, peak summer for July-driven heat, or deep winter for January-driven cold. All figures here are thirty-year averages: any single year may run warmer, wetter, drier, or cooler than the normal, so treat them as planning guidance rather than forecasts.
Frequently Asked Questions
What is the average temperature in Harrisburg, IL? ▼
The average annual temperature in Harrisburg, Illinois is 57°F. The warmest month averages 89°F (32°C) and the coldest averages 24°F (-4°C).
How much rain does Harrisburg get? ▼
Harrisburg receives 47.6 inches of precipitation annually. Based on NOAA 30-year climate normals (1991-2020).
What is the comfort score for Harrisburg? ▼
Harrisburg has a climate comfort score of 78/100 (Good), milder than 74% of U.S. cities in the PlainClimate database.
When is the growing season in Harrisburg? ▼
Harrisburg has approximately 202 frost-free days per year, with the last spring freeze around April 7 and the first fall freeze around October 26.
How much energy does heating and cooling require in Harrisburg? ▼
Harrisburg has 4,299 heating degree days and 1,522 cooling degree days annually, a heating-dominated climate. See our <a href="/guides/reading-weather-data/" class="underline hover:text-brand-600">guide to reading weather data</a> for what these figures mean.
Where does this Harrisburg climate data come from? ▼
NOAA U.S. Climate Normals v1.0.1 (1991-2020), from weather station USC00113879 near Harrisburg.
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). Station: USC00113879. For informational purposes only.
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainClimate Editorial
Every figure on PlainClimate is rendered directly from NOAA 1991-2020 U.S. Climate Normals data, no number is typed in by an editor. This page draws directly on NOAA 1991-2020 U.S. Climate Normals data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.