Alamosa, CO 81101 Frost Dates
Alamosa, CO: when does the frost end?
Around 05/30 is the usual last spring frost, about 275 days away. Fall's first freeze usually shows up around 09/17, roughly 108 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Alamosa in Zone 4b (-25 to -20°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
With roughly 3 weeks until Alamosa's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/30 isn't a guarantee
05/30 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/17 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/13 and only about 1 year in 10 sees frost after that.
Alamosa against the rest of the dataset
At roughly 108 frost-free days, Alamosa places 39,534 of 40,283 ZIP codes in this dataset. Within CO, it ranks 511 of 624.
Learn more
Before leaning on 81101's figures: the frost range explains how to read the range around Alamosa's dates instead of trusting one, while local microclimates explains what one yard in Alamosa can differ from the 81101 normal.