Thornton, CO 80241 Frost Dates
Thornton, CO: when does the frost end?
The last spring frost here typically falls around 05/02, about 247 days from today. Fall's first freeze usually shows up around 10/11, roughly 160 days after the last spring frost.
Thornton sits in USDA Zone 6a (-10 to -5°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
With roughly 6 weeks until Thornton's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Thornton's last frost
05/02 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/18 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/14 and only about 1 year in 10 sees frost after that.
Thornton against the rest of the dataset
At roughly 160 frost-free days, Thornton places 32,188 of 40,283 ZIP codes in this dataset. Within CO, it ranks 86 of 624.
Learn more
Before leaning on 80241's figures: local microclimates explains what one yard in Thornton can differ from the 80241 normal, while zone vs. frost date explains why Zone 6a and Thornton's frost date answer different questions.