Climate Comfort Score
68/100
Good
NOAA 1991–2020 normals 53°F annual avg Public-domain federal data
Sullivan, IL Climate
Explore average temperature, rainfall, and comfort score sourced from NOAA NCEI's 1991–2020 climate normals →
- 53°F
- Avg annual temp
- 68/100
- Comfort score
- 41.6"
- Annual precip
- 190d
- Growing season
30-year climate normals from 1 weather station (1991-2020).
The climate verdict for Sullivan
Sullivan, Illinois averages 53°F a year and scores 68/100 on the comfort index - good, milder than 58% of U.S. cities.
- 53°F
- average temperature, NOAA 1991-2020 normal
- 68/100
- comfort score, milder than 58% of U.S. cities
- 41.6"
- annual precipitation · 13" snow
- 190 days
- growing season, frost-free days
Based on NOAA U.S. Climate Normals (1991–2020) - 30-year averages describing the typical year, not a forecast.
Avg Temperature
53°F (12°C)
Avg High
63°F
Avg Low
43°F
Annual Precip
41.6"
Annual Snow
12.9"
Comfort Score
68/100
Good
Avg Annual Temperature
53°F
30-year mean (NOAA NCEI)
Annual Precipitation
41.6"
Plus 12.9" of snow
Comfort score vs national 100-point ceiling (Sullivan) 68.0%
National median (63)
PlainClimate composite, temperature mildness, humidity, precipitation, extreme-weather frequency. Good for the Sullivan area.
How Sullivan compares to every U.S. city
Sullivan's comfort score vs. all U.S. cities
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
68 Top 42% higher than 58% 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 Sullivan
MethodologyZooming out from Sullivan's own normal, the chart below shows how the U.S. land temperature anomaly has tracked the global mean since 1900 - the most recent decade sits warmer than the 30-year mean shown here.
- 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 | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 35°F (2°C) | 19°F (-7°C) | 27°F (-3°C) | 2.4" | 5.2" | 27.8 | 0.0 |
| February | 40°F (5°C) | 22°F (-6°C) | 31°F (-1°C) | 2.2" | 2.4" | 24.3 | 0.0 |
| March | 51°F (11°C) | 31°F (0°C) | 41°F (5°C) | 2.8" | 1.0" | 19.2 | 0.0 |
| April | 65°F (18°C) | 42°F (5°C) | 53°F (12°C) | 4.5" | 0.2" | 5.9 | 0.0 |
| May | 75°F (24°C) | 53°F (12°C) | 64°F (18°C) | 5.0" | 0.0" | 0.2 | 0.6 |
| June | 83°F (28°C) | 63°F (17°C) | 73°F (23°C) | 5.0" | 0.0" | 0.0 | 4.4 |
| July | 86°F (30°C) | 65°F (18°C) | 76°F (24°C) | 4.3" | 0.0" | 0.0 | 7.8 |
| August | 85°F (30°C) | 62°F (17°C) | 74°F (23°C) | 3.2" | 0.0" | 0.0 | 5.5 |
| September | 80°F (27°C) | 55°F (13°C) | 67°F (20°C) | 2.7" | 0.0" | 0.0 | 3.6 |
| October | 67°F (20°C) | 44°F (7°C) | 56°F (13°C) | 3.3" | 0.0" | 4.0 | 0.2 |
| November | 52°F (11°C) | 33°F (1°C) | 43°F (6°C) | 3.5" | 0.4" | 15.1 | 0.0 |
| December | 40°F (5°C) | 25°F (-4°C) | 32°F (0°C) | 2.8" | 3.7" | 25.4 | 0.0 |
Monthly Precipitation
Average monthly rainfall and snowfall
January 2.4"
Snow: 5.2"
8.0 days with precipitation
February 2.2"
Snow: 2.4"
7.9 days with precipitation
March 2.8"
Snow: 1.0"
8.5 days with precipitation
April 4.5"
Snow: 0.2"
10.1 days with precipitation
May 5.0"
11.9 days with precipitation
June 5.0"
10.0 days with precipitation
July 4.3"
8.1 days with precipitation
August 3.2"
6.9 days with precipitation
September 2.7"
6.7 days with precipitation
October 3.3"
8.3 days with precipitation
November 3.5"
Snow: 0.4"
8.5 days with precipitation
December 2.8"
Snow: 3.7"
8.1 days with precipitation
Frost Dates & Growing Season
First Fall Freeze
October 22
50% probability date
Last Spring Freeze
April 15
50% probability date
Growing Season
190 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
5,449
Higher = more heating needed
Cooling Degree Days
1,128
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
What Sullivan's climate means for you
Sullivan runs 53°F a year - peaking in July, coldest in January.
- Gardeners get about 190 frost-free days, with the last spring freeze near April 15 - plan the planting calendar around it, not the regional average.
- Energy bills track 5,449 heating and 1,128 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: Sullivan, IL
Sullivan, Illinois runs an annual average of 53°F, ranging from a mean daily high of 63°F to a mean daily low of 43°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 USC00118389, 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. Sullivan receives roughly 41.6 inches of precipitation each year, with 12.9 inches typically falling as snow. The frost-free season averages 190 days, which directly shapes the planting calendar and growing potential for the area, with the last spring freeze near April 15 and the first fall freeze near October 22. For energy use, 5,449 heating degree days and 1,128 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.
On PlainClimate's composite comfort index, Sullivan scores 68/100 (Good), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. For planning purposes, look to the monthly tables above: shoulder seasons bring the mildest highs and lows, summer brings July-driven heat, and deep winter brings January-driven cold. Treat every figure here as a thirty-year average rather than a forecast - individual years routinely run warmer, cooler, wetter, or drier than the normal.
Frequently Asked Questions
What is the average temperature in Sullivan, IL? ▼
The average annual temperature in Sullivan, Illinois is 53°F. The warmest month averages 86°F (30°C) and the coldest averages 19°F (-7°C).
How much rain does Sullivan get? ▼
Sullivan receives 41.6 inches of precipitation annually, including 12.9 inches of snow. Based on NOAA 30-year climate normals (1991-2020).
What is the comfort score for Sullivan? ▼
Sullivan has a climate comfort score of 68/100 (Good), milder than 58% of U.S. cities in the PlainClimate database.
When is the growing season in Sullivan? ▼
Sullivan has approximately 190 frost-free days per year, with the last spring freeze around April 15 and the first fall freeze around October 22.
How much energy does heating and cooling require in Sullivan? ▼
Sullivan has 5,449 heating degree days and 1,128 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 Sullivan climate data come from? ▼
NOAA U.S. Climate Normals v1.0.1 (1991-2020), from weather station USC00118389 near Sullivan.
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). Station: USC00118389. 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.