Climate Comfort Score
63/100
Good
NOAA 1991–2020 normals 50°F annual avg Public-domain federal data
Ottawa, IL Climate
Pulled from NOAA NCEI 1991–2020 normals →: average temperature, precipitation, and comfort score
- 50°F
- Avg annual temp
- 63/100
- Comfort score
- 36.2"
- Annual precip
- 185d
- Growing season
30-year climate normals from 1 weather station (1991-2020).
The climate verdict for Ottawa
Ottawa, Illinois averages 50°F a year and scores 63/100 on the comfort index - good, milder than 47% of U.S. cities.
- 50°F
- yearly average temperature, NOAA normal
- 63/100
- comfort score, milder than 47% of U.S. cities
- 36.2"
- annual precipitation · 24" snow
- 185 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
50°F (10°C)
Avg High
60°F
Avg Low
41°F
Annual Precip
36.2"
Annual Snow
23.7"
Comfort Score
63/100
Good
Avg Annual Temperature
50°F
30-year mean (NOAA NCEI)
Annual Precipitation
36.2"
Plus 23.7" of snow
Comfort score vs national 100-point ceiling (Ottawa) 63.0%
National median (63)
PlainClimate composite, temperature mildness, humidity, precipitation, extreme-weather frequency. Good for the Ottawa area.
How Ottawa compares to every U.S. city
Ottawa's comfort score vs. all U.S. cities
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
63 Top 53% higher than 47% 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 Ottawa
MethodologyThe chart below traces how the U.S. land temperature anomaly has moved against the global mean since 1900. For Ottawa, the NOAA 1991-2020 normal captures average conditions across that spread - notably, the most recent decade runs warmer than the 30-year mean itself.
- 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 | 31°F (-1°C) | 15°F (-9°C) | 23°F (-5°C) | 1.8" | 9.2" | 28.6 | 0.0 |
| February | 35°F (2°C) | 19°F (-7°C) | 27°F (-3°C) | 1.5" | 5.2" | 25.1 | 0.0 |
| March | 48°F (9°C) | 29°F (-2°C) | 38°F (3°C) | 2.3" | 3.3" | 21.1 | 0.0 |
| April | 61°F (16°C) | 39°F (4°C) | 50°F (10°C) | 3.5" | 0.4" | 6.2 | 0.1 |
| May | 72°F (22°C) | 51°F (11°C) | 61°F (16°C) | 4.5" | 0.0" | 0.3 | 0.8 |
| June | 80°F (27°C) | 61°F (16°C) | 70°F (21°C) | 4.4" | 0.0" | 0.0 | 3.7 |
| July | 83°F (28°C) | 64°F (18°C) | 74°F (23°C) | 3.6" | 0.0" | 0.0 | 5.6 |
| August | 82°F (28°C) | 62°F (17°C) | 72°F (22°C) | 3.7" | 0.0" | 0.0 | 4.5 |
| September | 76°F (25°C) | 54°F (12°C) | 65°F (19°C) | 3.2" | 0.0" | 0.1 | 2.5 |
| October | 64°F (18°C) | 43°F (6°C) | 53°F (12°C) | 3.1" | 0.0" | 3.6 | 0.1 |
| November | 49°F (9°C) | 32°F (0°C) | 40°F (4°C) | 2.5" | 0.8" | 16.9 | 0.0 |
| December | 36°F (2°C) | 21°F (-6°C) | 29°F (-2°C) | 2.0" | 4.8" | 27.0 | 0.0 |
Monthly Precipitation
Average monthly rainfall and snowfall
January 1.8"
Snow: 9.2"
8.7 days with precipitation
February 1.5"
Snow: 5.2"
7.5 days with precipitation
March 2.3"
Snow: 3.3"
9.0 days with precipitation
April 3.5"
Snow: 0.4"
11.6 days with precipitation
May 4.5"
12.2 days with precipitation
June 4.4"
10.6 days with precipitation
July 3.6"
8.4 days with precipitation
August 3.7"
8.8 days with precipitation
September 3.2"
8.2 days with precipitation
October 3.1"
9.4 days with precipitation
November 2.5"
Snow: 0.8"
8.6 days with precipitation
December 2.0"
Snow: 4.8"
8.6 days with precipitation
Frost Dates & Growing Season
First Fall Freeze
October 22
50% probability date
Last Spring Freeze
April 20
50% probability date
Growing Season
185 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
6,211
Higher = more heating needed
Cooling Degree Days
865
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
What Ottawa's climate means for you
Ottawa runs 50°F a year - peaking in July, coldest in January.
- Gardeners get about 185 frost-free days, with the last spring freeze near April 20 - plan the planting calendar around it, not the regional average.
- Energy bills track 6,211 heating and 865 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: Ottawa, IL
The NOAA 1991–2020 climate normals describe Ottawa, Illinois as a location with an annual average temperature of 50°F, ranging from a mean daily high of 60°F to a mean daily low of 41°F. July is typically the warmest month of the year, while January is the coldest. These thirty-year averages, computed from station USC00116526, smooth out year-to-year variability and give a baseline expectation for typical conditions in any given month.
Precipitation patterns matter as much as temperature for anyone planning to live, garden, or travel here. Ottawa receives roughly 36.2 inches of precipitation each year, with 23.7 inches typically falling as snow. The frost-free season averages 185 days, which directly shapes the planting calendar and growing potential for the area, with the last spring freeze near April 20 and the first fall freeze near October 22. For energy use, 6,211 heating degree days and 865 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.
On PlainClimate's composite comfort index, Ottawa scores 63/100 (Good), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. Shoulder seasons bring the mildest highs and lows in the monthly tables above, summer brings July-driven heat, and winter brings January-driven cold - use that rhythm for planning. These figures are thirty-year averages rather than forecasts, so a specific year may still run warmer, cooler, wetter, or drier than what's shown.
Frequently Asked Questions
What is the average temperature in Ottawa, IL? ▼
The average annual temperature in Ottawa, Illinois is 50°F. The warmest month averages 83°F (28°C) and the coldest averages 15°F (-9°C).
How much rain does Ottawa get? ▼
Ottawa receives 36.2 inches of precipitation annually, including 23.7 inches of snow. Based on NOAA 30-year climate normals (1991-2020).
What is the comfort score for Ottawa? ▼
Ottawa has a climate comfort score of 63/100 (Good), milder than 47% of U.S. cities in the PlainClimate database.
When is the growing season in Ottawa? ▼
Ottawa has approximately 185 frost-free days per year, with the last spring freeze around April 20 and the first fall freeze around October 22.
How much energy does heating and cooling require in Ottawa? ▼
Ottawa has 6,211 heating degree days and 865 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 Ottawa climate data come from? ▼
NOAA U.S. Climate Normals v1.0.1 (1991-2020), from weather station USC00116526 near Ottawa.
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). Station: USC00116526. 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.