Thornton has chilly winters and pleasant summers. A typical July afternoon reaches 84°, a January night drops to 18°, and about 28 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normalsUpdated once a decade
☀️
July high
84°
504th coolest of 2,886 Illinois towns
❄️
January low
18°
1364th mildest of 2,886 Illinois towns
💧
Rain + melted snow
39 in
1219th driest of 2,886 Illinois towns
🌨️
Snow a winter
28 in
738th snowiest of 2,880 Illinois towns
A normal year
What a year in Thornton feels like
❄️
Winter
35° / 20°
Typical high / low · 13 days with an inch or more of snow
🌷
Spring
59° / 39°
Typical high / low · Last frost around Apr 23
☀️
Summer
82° / 62°
Typical high / low · 16 days reach 90° in a normal year
🍂
Fall
63° / 44°
Typical high / low · First frost around Oct 20
0°
10°
20°
40°
50°
60°
70°
80°
90°
100°
32°
32°
18°
36°
21°
48°
29°
60°
39°
71°
49°
80°
59°
84°
64°
82°
62°
76°
55°
64°
43°
49°
33°
37°
23°
JanJFebFMarMAprAMayMJunJJulJAugASepSOctONovNDecD
32°, freezingBar runs from the typical overnight low up to the afternoon high
Best months to be outsideMayJunJulAugSepOctHighs of 62–84° and lows of 40° or more
Month by month
Thornton weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
Month
High
Low
Rain + melt
Snow
Wet days
Snow on ground
30-yr range
January
32°
18°
2.2"
10.2"
11
18
16° – 37°
February
36°
21°
1.9"
7.5"
9
13
17° – 39°
March
48°
29°
2.4"
4.9"
10
5
30° – 53°
April
60°
39°
3.8"
0.5"
12
0
41° – 55°
May
71°
49°
4.3"
0
13
0
54° – 67°
June
80°
59°
4.3"
0
10
0
65° – 74°
July
84°
64°
4.1"
0
9
0
69° – 79°
August
82°
62°
4.0"
0
9
0
67° – 78°
September
76°
55°
3.4"
0
8
0
59° – 70°
October
64°
43°
3.5"
0.2"
11
0
49° – 59°
November
49°
33°
2.7"
0.9"
10
1
34° – 49°
December
37°
23°
2.1"
4.0"
11
9
17° – 40°
Year
60°
41°
38.6"
28.2"
124
46
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain & snow
Rain and snow in Thornton
Thornton gets 39 inches of rain and melted snow a year. June is the wettest month and February the driest. Rain or snow falls on about 124 days a year. Snow covers the ground about 46 days of the year.
💧
39 in
Rain + melted snow a year
Less rain than 54% of U.S. towns
❄️
28 in
Snow in a normal winter
More snow than 55% of U.S. towns
⛄
46 days
With 1"+ of snow on the ground
More than 64% of U.S. towns
Rain + melted snow by month
Inches of water
4.3"
JFMAMJJASOND
Snowfall by month
Inches of snow
10"
JFMAMJJASOND
Frost & the growing season
About 179 frost-free days a year
In half of years the last 32° night comes by April 23 and the first one by October 20. That leaves about 179 frost-free days for gardens, longer than 51% of U.S. towns.
🌱 Apr 23
🍂 Oct 20
179 frost-free days
JFMAMJJASOND
🥶
126
nights at or below 32° in a normal year
🧊
8
nights below 0° in a normal year
🔥
16
days that reach 90° in a normal year
Freezing nights by month
Average nights at or below 32°
JFMAMJJASOND
90° days by month
Average days at 90° or more
JFMAMJJASOND
Heating & cooling
Heating and cooling a home in Thornton
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Thornton, 88% of that work is heating and 12% is cooling, so the furnace matters far more than the air conditioner.
🔥
6,350 heating degree daysMore heating than 63% of U.S. towns
❄️
859 cooling degree daysMore cooling than 51% of U.S. towns
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Around Thornton
Thornton and its neighbors
Thornton borders 12 towns with climate data. January nights across them vary by 1.1°. Bloom has the coldest January nights (17°) and Dixmoor the hottest July afternoons (84°). Thornton’s January low is 18° and its July high 84°.
Compared with every U.S. town and city on TownTapestry, each counted once.
Then and now
Warmer than it used to be
+1.2°1991–2020 average vs. the 20th century (1901–2000)
The last 30 years in Thornton averaged 1.2° warmer than the 1900s. The biggest change is in December (+2.5°). The shift is smaller than in 54% of U.S. towns.
❄️ Winter+2.0°now 28°, was 26°
🌷 Spring+1.3°now 49°, was 48°
☀️ Summer+0.5°now 72°, was 71°
🍂 Fall+0.9°now 53°, was 52°
Change by month1991–2020 average minus 1901–2000 average, at Thornton’s spot on NOAA’s grid
+0.3°
+2.5°
JanJFebFMarMAprAMayMJunJJulJAugASepSOctONovNDecD
Year to year
How much a month can swing
A normal is an average, and real years wander around it. March swings the most: between 1991 and 2020 its average temperature ranged from 30° to 53°. June is the most reliable, staying within 9°.
10°
20°
30°
40°
50°
60°
70°
80°
90°
JanJFebFMarMAprAMayMJunJJulJAugASepSOctONovNDecD
Coldest to warmest month in 30 yearsNormal
Questions
Common questions about Thornton’s climate
What is the coldest month in Thornton?
January, with a typical high of 32° and a low of 18°.
What is the hottest month in Thornton?
July, with a typical high of 84° and a low of 64°. About 16 days a year reach 90°.
How much snow does Thornton get?
About 28 inches in a normal winter, most of it in January.
When is the first frost in Thornton?
In half of years the first 32° night comes by October 20, and the last spring frost by April 23.
What is the rainiest month in Thornton?
June, with 4.3 inches of rain and melted snow. The year totals 39 inches.
📍Temperatures and rainfall come from NOAA’s gridded climate normals for Thornton itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Park Forest, IL (8 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.