U.S. Frost Dates by Weather Station

NOAA station USC00217326 · Minnesota

Frost Dates for Saint James, MN

NOAA weather station St. James WWTP (USC00217326), Minnesota · elevation 1070 ft (326 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 13only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% chance of a frost after it
  • Typical first fall frostOctober 750% chance of a frost before it
  • Frost-free season160 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Saint James, MNSpring: a frost after April 15 in 9 years out of 10, after April 30 in half of the years, after May 13 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 20 in 9 years out of 10. Typical frost-free season: 160 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 30First frost ~Oct 7Frost season at Saint James, MNSpring: a frost after April 15 in 9 years out of 10, after April 30 in half of the years, after May 13 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 20 in 9 years out of 10. Typical frost-free season: 160 days.JFMAMJJASONDLast frost ~Apr 30First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 13September 25
50% (typical)April 30October 7
90% (likely)April 15October 20
Frost-free season (32°F, 50% chance)
160 days
Hard frost (28°F), last in spring, 50% chance after
April 18
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost April 29 (1 day earlier than the 30-year normal), typical first fall frost October 12 (5 days later). Frost-free season 165 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 Saint James: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 13, 20% May 8, 30% May 4, 40% May 2, 50% April 30, 60% April 27, 70% April 23, 80% April 20, 90% April 15. Observed last spring frost in recent years: 2021 May 11, 2022 April 27, 2023 April 27, 2024 April 24, 2025 April 20, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 13Apr 30Apr 152021: May 112022: April 272023: April 272024: April 242025: April 202026: May 7Fall at Saint James: chance of a frost before this dateFall, chance of a frost before the date: 10% September 25, 20% September 29, 30% October 1, 40% October 4, 50% October 7, 60% October 10, 70% October 13, 80% October 15, 90% October 20. Observed first fall frost in recent years: 2021 October 23, 2022 September 28, 2023 October 11, 2024 October 15, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 25Oct 7Oct 202021: October 232022: September 282023: October 112024: October 152025: October 8
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 23
2022April 27September 28
2023April 27October 11
2024April 24October 15
2025April 20October 8
2026May 7season not over yet

What these dates mean

The 160 days between the 50% dates in Saint James mark the window that brackets the median risk of a light frost. The 50% date of April 30 in spring and the 50% date of October 7 in fall each represent an even-odds point, meaning there is a 50 % chance of a frost later than April 30 and a 50 % chance of a frost earlier than October 7; they are not themselves frost dates.

For a cautious planting plan, gardeners should wait until the May 13 date in spring, which carries only a 10 % chance of a frost later, before setting out tender crops. In the fall, the September 25 date is the cautious cutoff, with only a 10 % chance that a frost has arrived earlier, signalling when to finish harvesting tender crops. Hard frost at 28 °F, noted by the median dates of April 18 and October 17, can damage plants that survive a light frost at 32 °F, so it represents a greater threat.

How to read the probabilities

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

  • Spring: "10% after May 13" 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 Saint James, MNNumbered nearest stations: 1 — Amboy, MN — 23 mi; 2 — Windom, MN — 26 mi; 3 — Winnebago, MN — 27 mi; 4 — Lamberton SW Research & Outreach C, MN — 39 mi; 5 — St. Peter, MN — 39 mi.25 mi · 40 km1. Amboy, MN — 23 mi12. Windom, MN — 26 mi23. Winnebago, MN — 27 mi34. Lamberton SW Research & Outreach C, MN — 39 mi45. St. Peter, MN — 39 mi5
  1. Amboy, MN 23 mi (38 km)
  2. Windom, MN 26 mi (42 km)
  3. Winnebago, MN 27 mi (44 km)
  4. Lamberton SW Research & Outreach C, MN 39 mi (63 km)
  5. St. Peter, 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: 43.9903, -94.6122.