U.S. Frost Dates by Weather Station

NOAA station USC00217405 · Minnesota

Frost Dates for St. Peter, MN

NOAA weather station St. Peter (USC00217405), Minnesota · elevation 795 ft (242 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 450% chance of a frost before it
  • Frost-free season153 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at St. Peter, MNSpring: a frost after April 19 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 153 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 4Frost season at St. Peter, MNSpring: a frost after April 19 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 21 in 1 year out of 10, before October 4 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 153 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 4
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 14September 21
50% (typical)May 2October 4
90% (likely)April 19October 16
Frost-free season (32°F, 50% chance)
153 days
Hard frost (28°F), last in spring, 50% chance after
April 22
Hard frost (28°F), first in fall, 50% chance before
October 13

The last 15 years (2006–2020 normals)

Typical last frost May 1 (1 day earlier than the 30-year normal), typical first fall frost October 9 (5 days later). Frost-free season 159 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 at St. Peter: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 9, 30% May 6, 40% May 3, 50% May 2, 60% April 30, 70% April 27, 80% April 24, 90% April 19. Observed last spring frost in recent years: 2021 May 12, 2022 April 28, 2023 May 4, 2024 April 24, 2025 May 3.Spring: last frostChance of a frost after this date10%50%90%May 1May 14May 2Apr 192021: May 122022: April 282023: May 42024: April 242025: May 3Fall at St. Peter: chance of a frost before this dateFall, chance of a frost before the date: 10% September 21, 20% September 26, 30% September 29, 40% October 1, 50% October 4, 60% October 6, 70% October 9, 80% October 12, 90% October 16. Observed first fall frost in recent years: 2021 October 22, 2022 September 12, 2023 October 10, 2024 October 14.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 21Oct 4Oct 162021: October 222022: September 122023: October 102024: October 14
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 12October 22
2022April 28September 12
2023May 4October 10
2024April 24October 14
2025May 3incomplete record
2026incomplete recordseason not over yet

What these dates mean

The cautious fall date for finishing the tender-crop harvest in St. Peter is September 21, when there is only a 10 % chance that a light frost has already arrived.

For a gardener, the 50 % light-frost dates—May 2 in spring and October 4 in fall—mark the point at which the odds of a frost are even, so planting or harvesting around those days carries an equal chance of frost later (spring) or earlier (fall). A cautious spring schedule therefore waits until the late-season date of May 14, which carries only a 10 % chance of a frost later, while a cautious fall plan aims to finish by the early-season date of September 21, which carries only a 10 % chance of a frost earlier.

A hard frost at 28 °F is more damaging than a light frost at 32 °F because it can injure plant tissue that survives the milder temperature.

How to read the probabilities

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

  • Spring: "10% after May 14" 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 21" 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 St. Peter, MNNumbered nearest stations: 1 — Gaylord, MN — 21 mi; 2 — near Waseca, MN — 28 mi; 3 — Jordan, MN — 28 mi; 4 — Amboy, MN — 32 mi; 5 — Saint James, MN — 39 mi.IAWI25 mi · 40 km1. Gaylord, MN — 21 mi12. near Waseca, MN — 28 mi23. Jordan, MN — 28 mi34. Amboy, MN — 32 mi45. Saint James, MN — 39 mi5
  1. Gaylord, MN 21 mi (33 km)
  2. near Waseca, MN 28 mi (45 km)
  3. Jordan, MN 28 mi (45 km)
  4. Amboy, MN 32 mi (51 km)
  5. Saint James, MN 39 mi (63 km)

Sources

* Hardiness zone 5a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 44.3222, -93.9656.