St. Johns, AZ 87315 Frost Dates
87315, near St. Johns, AZ: the frost window
Typically, the last spring freeze lands around 05/31, roughly 276 days out. Fall's first freeze usually shows up around 10/01, roughly 122 days after the last spring frost.
St. Johns 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
St. Johns's growing season runs out in roughly 5 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
How much risk comes with planting early here
05/31 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/15 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/15 and only about 1 year in 10 sees frost after that.
St. Johns against the rest of the dataset
St. Johns's growing season runs about 122 days, ranking 38,935 of 40,283 US ZIP codes measured here, longest to shortest. Within AZ, it ranks 493 of 506.
Learn more
Two guides worth reading on 87315: local microclimates, on what one yard in St. Johns can differ from the 87315 normal, and zone vs. frost date, on why Zone 6a and St. Johns's frost date answer different questions.