Thornton, CO Weather by Month and Climate Averages

How much rain does Thornton get?

Thornton gets 14.5 in of precipitation in an average year, spread over about 73 days with measurable rain. That is fewer rainy days than 65% of the US.

May is the wettest month, with 2.4 in. January is the driest, with 0.5 in. May has the most rainy days, about 10.

The longest dry spell in the last five years lasted 25 days, to October 18, 2024.

See where Thornton ranks: rainiest cities in the US, US cities with the most rainy days, rainiest cities in Colorado.

Does it snow in Thornton?

Yes. Thornton gets about 44.8 in of snow in an average season, measured at the reporting station.

The snowiest winter on record is 1972–73, with 95.1 in.

The most recent measurable snow at the station fell on May 6, 2026.

See where Thornton ranks: snowiest cities in the US.

Thornton weather by month

Thornton weather in January

In January, Thornton averages a high of 47°F and a low of 19°F. It gets 0.5 in of precipitation over about 4 rainy days. The sun is out about 55% of daylight hours. The January record high is 77°F (1997) and the record low is -15°F (1985).

Thornton weather in February

In February, Thornton averages a high of 49°F and a low of 21°F. It gets 0.5 in of precipitation over about 4 rainy days. The sun is out about 57% of daylight hours. The February record high is 83°F (2017) and the record low is -17°F (1996).

Thornton weather in March

In March, Thornton averages a high of 58°F and a low of 28°F. It gets 1.2 in of precipitation over about 5 rainy days. The sun is out about 52% of daylight hours. The March record high is 94°F (2026) and the record low is -5°F (2002).

Thornton weather in April

In April, Thornton averages a high of 64°F and a low of 35°F. It gets 1.9 in of precipitation over about 8 rainy days. The sun is out about 55% of daylight hours. The April record high is 90°F (2025) and the record low is 6°F (1997). April is one of the most comfortable months to visit.

Thornton weather in May

In May, Thornton averages a high of 73°F and a low of 44°F. It gets 2.4 in of precipitation over about 10 rainy days. The sun is out about 48% of daylight hours. The May record high is 101°F (2003) and the record low is 20°F (2013).

Thornton weather in June

In June, Thornton averages a high of 84°F and a low of 53°F. It gets 1.5 in of precipitation over about 7 rainy days. The sun is out about 53% of daylight hours. The June record high is 105°F (2018) and the record low is 34°F (1988).

Thornton weather in July

In July, Thornton averages a high of 91°F and a low of 59°F. It gets 1.7 in of precipitation over about 7 rainy days. The sun is out about 59% of daylight hours. The July record high is 108°F (2005) and the record low is 43°F (1987).

Thornton weather in August

In August, Thornton averages a high of 88°F and a low of 57°F. It gets 1.3 in of precipitation over about 8 rainy days. The sun is out about 60% of daylight hours. The August record high is 110°F (2008) and the record low is 41°F (1986).

Thornton weather in September

In September, Thornton averages a high of 80°F and a low of 49°F. It gets 1.2 in of precipitation over about 6 rainy days. The sun is out about 70% of daylight hours. The September record high is 102°F (2019) and the record low is 18°F (1985).

Thornton weather in October

In October, Thornton averages a high of 67°F and a low of 37°F. It gets 1.1 in of precipitation over about 5 rainy days. The sun is out about 69% of daylight hours. The October record high is 93°F (2024) and the record low is 4°F (2019). October is one of the most comfortable months to visit.

Thornton weather in November

In November, Thornton averages a high of 55°F and a low of 27°F. It gets 0.7 in of precipitation over about 5 rainy days. The sun is out about 65% of daylight hours. The November record high is 84°F (2025) and the record low is -6°F (1993).

Thornton weather in December

In December, Thornton averages a high of 47°F and a low of 19°F. It gets 0.5 in of precipitation over about 4 rainy days. The sun is out about 62% of daylight hours. The December record high is 82°F (2025) and the record low is -24°F (1990).

Sunshine, humidity and wind in Thornton

September is the sunniest month in Thornton, with sunshine about 70% of daylight hours. May is the cloudiest, at 48%. Over the year the sun shines about 59% of daylight hours. Thornton is sunnier than 84% of the US.

Humidity peaks in January at 57% and is lowest in September at 37%.

Thornton has about 50 days a year above 90°F. Thornton is hotter than 69% of the US.

Thunderstorms occur on about 12 days a year.

See where Thornton ranks: sunniest cities in the US, cloudiest cities in the US, hottest cities in the US.

First and last freeze in Thornton

The first fall freeze in Thornton typically comes around October 7, and the last spring freeze around May 4. That leaves a frost-free growing season of about 156 days.

Thornton weather records

The hottest temperature on record at the Thornton station is 110°F, on August 2, 2008. The coldest is -24°F, on December 22, 1990.

The wettest day on record brought 2.5 in of rain, on August 24, 1992.

45 all-time records have been set at the station since 1984.

The annual mean temperature has changed by +1.0°F per decade since 1985.

The best time to visit Thornton

The most comfortable time to visit is typically April and October, when daytime highs sit near 66°F.

Winter (December–February) is chilly, with average highs around 48°F and lows near 20°F. Snow is possible.

Spring (March–May) is mild, with average highs around 65°F and lows near 36°F.

Summer (June–August) is hot, with average highs around 88°F and lows near 56°F.

Autumn (September–November) is mild, with average highs around 68°F and lows near 37°F.

Thornton climate questions

How much rain does Thornton get?

Thornton gets 14.5 in of precipitation in an average year, over about 73 rainy days.

What is the wettest month in Thornton?

May is the wettest month in Thornton, with 2.4 in. January is the driest, with 0.5 in.

How many rainy days does Thornton have a year?

Thornton has about 73 days with measurable rain in an average year. May has the most, about 10.

Does it snow in Thornton?

Yes. Thornton gets about 44.8 in of snow in an average season. The snowiest winter on record is 1972–73, with 95.1 in.

What is the hottest month in Thornton?

July is the warmest month in Thornton, with an average high of 91°F.

What is the coldest month in Thornton?

January is the coldest month in Thornton, with an average low of 19°F.

What is the record high temperature in Thornton?

The record high at the Thornton station is 110°F, set on August 2, 2008. The record low is -24°F, on December 22, 1990.

What is the sunniest month in Thornton?

September is the sunniest month in Thornton, with sunshine about 70% of daylight hours. May is the cloudiest.

When is the first frost in Thornton?

The first fall freeze in Thornton typically comes around October 7. The last spring freeze is around May 4.

What is the best time to visit Thornton?

The most comfortable time to visit is typically April and October, when daytime highs sit near 66°F.