Colorado Frost Dates & Growing Zones by City

Across the 20 Colorado cities with frost dates on this site, the typical (50%) last spring frost runs from Apr 26 in Pueblo to May 10 in Loveland. The typical frost-free season runs from 142 days (Loveland) to 171 days (Grand Junction).

The 2023 USDA hardiness map places them in zones 5a, 5b, 6a, 6b and 7a.

Each city's dates come from the nearest NOAA station that passes our quality rules. The methodology explains how we pick it.

Colorado cities: NOAA 1991–2020 frost dates (typical = 50%) and USDA 2023 zones
City	Last frost (50%)	First frost (50%)	Season (days, 50%)	Zone 2023	Confidence	Planting calendar
Denver frost dates	Apr 30	Oct 12	165	6a	High	Denver planting calendar
Colorado Springs frost dates	May 3	Oct 8	158	5b–6a	High	Colorado Springs planting calendar
Aurora frost dates	May 7	Oct 8	152	6a	Medium	Aurora planting calendar
Fort Collins frost dates	May 2	Oct 7	157	5b	High	Fort Collins planting calendar
Lakewood frost dates	May 3	Oct 7	155	6a	High	Lakewood planting calendar
Thornton frost dates	May 2	Oct 11	160	6a	High	Thornton planting calendar
Arvada frost dates	May 5	Oct 5	151	6a	High	Arvada planting calendar
Westminster Same station and zone as Thornton	May 2	Oct 11	160	6a	High	–
Greeley frost dates	May 2	Oct 8	159	5a–5b	High	Greeley planting calendar
Pueblo frost dates	Apr 26	Oct 13	166	6a	High	Pueblo planting calendar
Centennial frost dates	May 5	Oct 8	154	6a	High	Centennial planting calendar
Boulder frost dates	May 6	Oct 5	151	6a	High	Boulder planting calendar
Longmont frost dates	May 7	Oct 5	151	5b–6a	Medium	Longmont planting calendar
Castle Rock frost dates	May 9	Oct 2	143	5b	High	Castle Rock planting calendar
Loveland frost dates	May 10	Oct 1	142	5b	High	Loveland planting calendar
Broomfield Same station and zone as Thornton	May 2	Oct 11	160	6a	High	–
Commerce City frost dates	May 3	Oct 7	155	5b	High	Commerce City planting calendar
Grand Junction frost dates	Apr 28	Oct 16	171	6b–7a	High	Grand Junction planting calendar
Parker frost dates	May 9	Oct 3	145	5b–6a	Medium	Parker planting calendar
Littleton frost dates	May 2	Oct 11	160	5b–6a	Medium	Littleton planting calendar

Station match, data and rules: methodology. Long-term odds, not a forecast.