U.S. Frost Dates by Weather Station

NOAA station USC00215615 · Minnesota

Frost Dates for Mora, MN

NOAA weather station Mora (USC00215615), Minnesota · elevation 1018 ft (310 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 950% chance of a frost after it
  • Typical first fall frostSeptember 3050% chance of a frost before it
  • Frost-free season142 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Mora, MNSpring: a frost after April 26 in 9 years out of 10, after May 9 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before September 30 in half of the years, before October 12 in 9 years out of 10. Typical frost-free season: 142 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Sep 30Frost season at Mora, MNSpring: a frost after April 26 in 9 years out of 10, after May 9 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before September 30 in half of the years, before October 12 in 9 years out of 10. Typical frost-free season: 142 days.JFMAMJJASONDLast frost ~May 9First frost ~Sep 30
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 26September 17
50% (typical)May 9September 30
90% (likely)April 26October 12
Frost-free season (32°F, 50% chance)
142 days
Hard frost (28°F), last in spring, 50% chance after
April 28
Hard frost (28°F), first in fall, 50% chance before
October 9

The last 15 years (2006–2020 normals)

Typical last frost May 5 (4 days earlier than the 30-year normal), typical first fall frost October 3 (3 days later). Frost-free season 148 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 Mora: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 20, 30% May 16, 40% May 12, 50% May 9, 60% May 6, 70% May 3, 80% April 30, 90% April 26. Observed last spring frost in recent years: 2021 May 30, 2022 May 4, 2023 May 4, 2024 April 24, 2025 May 4, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 9Apr 262021: May 302022: May 42023: May 42024: April 242025: May 42026: May 20Fall at Mora: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 21, 30% September 24, 40% September 27, 50% September 30, 60% October 1, 70% October 4, 80% October 7, 90% October 12. Observed first fall frost in recent years: 2021 October 18, 2022 September 28, 2023 October 9, 2024 October 4, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Sep 30Oct 122021: October 182022: September 282023: October 92024: October 42025: 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 30October 18
2022May 4September 28
2023May 4October 9
2024April 24October 4
2025May 4October 8
2026May 20season not over yet

What these dates mean

May 26 is the cautious spring light-frost date for Mora, carrying only a 10 % chance that a frost will occur later. Planting tender vegetables after this day gives a gardener a very low risk of a damaging light frost.

The 50% date is May 9, indicating a 50 % chance of a light frost later, while the 50% date of September 30 represents a 50 % chance of a light frost earlier. For a cautious fall plan, September 17 is the date with only a 10 % chance that a frost has already arrived, marking a reasonable point to finish harvesting tender crops. The hard-frost median dates are April 28 and October 9; hard frost at 28 °F can injure plant tissue that typically survives a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after May 26" 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 17" 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 Mora, MNNumbered nearest stations: 1 — Grantsburg, WI — 31 mi; 2 — Santiago, MN — 31 mi; 3 — Wild River State Park, MN — 37 mi; 4 — Saint Cloud, MN — 42 mi; 5 — Forest Lake, MN — 43 mi.MNWI25 mi · 40 km1. Grantsburg, WI — 31 mi12. Santiago, MN — 31 mi23. Wild River State Park, MN — 37 mi34. Saint Cloud, MN — 42 mi45. Forest Lake, MN — 43 mi5
  1. Grantsburg, WI 31 mi (50 km)
  2. Santiago, MN 31 mi (50 km)
  3. Wild River State Park, MN 37 mi (59 km)
  4. Saint Cloud, MN 42 mi (68 km)
  5. Forest Lake, MN 43 mi (69 km)

Sources

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

Station coordinates: 45.8775, -93.3147.