U.S. Frost Dates by Weather Station

NOAA station USC00211691 · Minnesota

Frost Dates near Collegeville, MN

NOAA weather station Collegeville St. John's (USC00211691), Minnesota · elevation 1210 ft (369 m) · hardiness zone 4b*

Collegeville is the nearest town to the station (1.7 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 750% chance of a frost before it
  • Frost-free season155 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season near Collegeville, MNSpring: a frost after April 21 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 7 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 155 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 7Frost season near Collegeville, MNSpring: a frost after April 21 in 9 years out of 10, after May 3 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 7 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 155 days.JFMAMJJASONDLast frost ~May 3First frost ~Oct 7
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17September 25
50% (typical)May 3October 7
90% (likely)April 21October 19
Frost-free season (32°F, 50% chance)
155 days
Hard frost (28°F), last in spring, 50% chance after
April 24
Hard frost (28°F), first in fall, 50% chance before
October 18

The last 15 years (2006–2020 normals)

Typical last frost May 3 (same as the 30-year normal), typical first fall frost October 10 (3 days later). Frost-free season 158 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring near Collegeville: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 12, 30% May 8, 40% May 5, 50% May 3, 60% April 30, 70% April 29, 80% April 26, 90% April 21. Observed last spring frost in recent years: 2021 May 11, 2022 April 28, 2023 April 26, 2024 April 22, 2025 April 20, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 3Apr 212021: May 112022: April 282023: April 262024: April 222025: April 202026: May 7Fall near Collegeville: chance of a frost before this dateFall, chance of a frost before the date: 10% September 25, 20% September 30, 30% October 2, 40% October 4, 50% October 7, 60% October 9, 70% October 12, 80% October 15, 90% October 19. Observed first fall frost in recent years: 2021 October 22, 2023 October 10, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 25Oct 7Oct 192021: October 222023: October 102025: October 23
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021May 11October 22
2022April 28incomplete record
2023April 26October 10
2024April 22incomplete record
2025April 20October 23
2026May 7season not over yet

What these dates mean

The 155 days between the 50% dates in the Collegeville area mark the period after the median chance of a light frost has passed in spring and before the median chance arrives in fall, providing the core window for tender crops. Gardeners see May 3 and October 7 as the 50% light-frost dates, meaning there is an even odds of a frost occurring later (spring) or earlier (fall) than those points.

For a cautious spring plan the date to set out tender crops is May 17, when only a 10% chance of a later frost remains; in fall the cautious date to finish harvesting tender crops is September 25, with a 10% chance that frost has already arrived. The 50% hard-frost dates are April 24 and October 18, and a hard frost at 28 °F can damage plants that survive a light frost at 32 °F because the lower temperature penetrates tissue more deeply.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after May 17" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before September 25" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Collegeville, MNNumbered nearest stations: 1 — Saint Cloud, MN — 17 mi; 2 — Santiago, MN — 31 mi; 3 — Litchfield, MN — 32 mi; 4 — Long Prairie, MN — 36 mi; 5 — Glenwood, MN — 51 mi.MN25 mi · 40 km1. Saint Cloud, MN — 17 mi12. Santiago, MN — 31 mi23. Litchfield, MN — 32 mi34. Long Prairie, MN — 36 mi45. Glenwood, MN — 51 mi5
  1. Saint Cloud, MN 17 mi (27 km)
  2. Santiago, MN 31 mi (50 km)
  3. Litchfield, MN 32 mi (51 km)
  4. Long Prairie, MN 36 mi (58 km)
  5. Glenwood, MN 51 mi (82 km)

Sources

* Hardiness zone 4b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 45.5794, -94.3919.