Thornton weather by month
Average highs run from 46°F in January to 90°F in July, and January nights average 18°F. It gets 15 inches of rain and melted snow a year and 49 inches of snow. Expect about 42 days a year at 90°F or hotter. Nights drop below freezing about 156 times a year. The most comfortable months are May to June and September.
Best time to visit Thornton
For comfortable weather, go in May to June and September. In those months the average high stays between 62°F and 86°F, nights average 42°F or warmer, and rain stays under 4.5 inches for the month.
Month by month
| Month | High | Low | Precip. | Snow | Wet days | Days 90°F+ | Nights below 32°F | Feels |
|---|---|---|---|---|---|---|---|---|
| January | 47°F | 18°F | 0.5 in | 6.4 in | 2 | 0 | 30 | cold |
| February | 48°F | 19°F | 0.5 in | 7.6 in | 2 | 0 | 26 | cold |
| March | 56°F | 27°F | 1.1 in | 8.8 in | 3 | 0 | 23 | cool |
| April | 63°F | 34°F | 1.7 in | 6.2 in | 4 | 0 | 12 | mild days, chilly nights |
| May | 72°F | 43°F | 2.3 in | 1.4 in | 5 | 1 | 2 | mild |
| June | 84°F | 53°F | 1.7 in | 0.0 in | 4 | 8 | 0 | warm |
| July | 90°F | 59°F | 2.1 in | 0.0 in | 4 | 17 | 0 | hot |
| August | 88°F | 57°F | 1.8 in | 0.0 in | 4 | 13 | 0 | hot |
| September | 80°F | 48°F | 1.5 in | 0.8 in | 3 | 4 | 1 | warm |
| October | 67°F | 36°F | 1.0 in | 3.9 in | 3 | 0 | 9 | mild days, chilly nights |
| November | 55°F | 26°F | 0.7 in | 7.3 in | 2 | 0 | 24 | cool |
| December | 46°F | 18°F | 0.5 in | 6.6 in | 2 | 0 | 30 | cold |
| Year | 66°F avg | 36°F avg | 15.4 in | 49.0 in | 38 | 42 | 156 |
"Wet days" are days with at least 0.1 inch of precipitation. "Feels" is a plain-language label for the average high. Normals for 1991-2020 from NOAA NCEI, station Denver-Stapleton, CO (USW00023062), 9.1 miles from the city center. Averages describe typical conditions, not a forecast.
Sunrise, sunset and daylight in Thornton
The shortest day is December 21, with 9h 20m of daylight; the longest is June 21, with 15h 00m. The earliest sunset comes around December 3 (4:34 pm) and the latest around June 24 (8:32 pm). The sun sets after 8 pm on 97 days a year.
| On the 15th of | Sunrise | Sunset | Daylight |
|---|---|---|---|
| January | 7:19 am | 4:59 pm | 9h 40m |
| February | 6:52 am | 5:35 pm | 10h 43m |
| March | 7:11 am | 7:06 pm | 11h 55m |
| April | 6:22 am | 7:38 pm | 13h 16m |
| May | 5:45 am | 8:07 pm | 14h 23m |
| June | 5:31 am | 8:29 pm | 14h 59m |
| July | 5:44 am | 8:26 pm | 14h 42m |
| August | 6:12 am | 7:55 pm | 13h 44m |
| September | 6:41 am | 7:08 pm | 12h 27m |
| October | 7:10 am | 6:19 pm | 11h 09m |
| November | 6:45 am | 4:43 pm | 9h 58m |
| December | 7:14 am | 4:35 pm | 9h 21m |
Calculated for 2026 at the center of Thornton with NOAA's solar equations, in local clock time (Mountain Time, including daylight saving time where it applies). Times shift by a minute or two from year to year.
Is Thornton getting warmer?
The last 10 years averaged 2.3°F warmer than the 20th century. See the climate stripes for Thornton.Frequently asked questions
What is the warmest month in Thornton?
July is the warmest month, with an average high of 90°F and an average low of 59°F (NOAA 1991-2020 normals).
What is the coldest month in Thornton?
January is the coldest, with average lows of 18°F and highs of 47°F.
What is the rainiest month in Thornton?
May gets the most precipitation, 2.3 inches on average. January is the driest at 0.5 inches.
Does it snow in Thornton?
Yes. Thornton averages 49 inches of snow a year.
When is the best time to visit Thornton?
For comfortable weather, May to June and September. Those months average highs between 62 and 86°F with lows of 42°F or more and modest rain.
Thinking of moving to Thornton?
See what homes, rent and everyday prices cost, who lives there and how it compares with nearby cities on the full Thornton profile.
Compare the weather: Thornton vs Westminster, Thornton vs Broomfield, Thornton vs Arvada, Thornton vs Denver.