U.S. Frost Dates by Weather Station

NOAA station USW00014910 · Minnesota

Frost Dates for Alexandria, MN

NOAA weather station Alexandria Municipal Airport (USW00014910), Minnesota · elevation 1416 ft (432 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 15only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 850% chance of a frost before it
  • Frost-free season159 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Alexandria, MNSpring: a frost after April 18 in 9 years out of 10, after May 2 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 8 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 159 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 8Frost season at Alexandria, MNSpring: a frost after April 18 in 9 years out of 10, after May 2 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 8 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 159 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 8
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 15September 27
50% (typical)May 2October 8
90% (likely)April 18October 20
Frost-free season (32°F, 50% chance)
159 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 19

The last 15 years (2006–2020 normals)

Typical last frost May 3 (1 day later than the 30-year normal), typical first fall frost October 12 (4 days later). Frost-free season 160 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 Alexandria: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 15, 20% May 10, 30% May 7, 40% May 4, 50% May 2, 60% April 30, 70% April 27, 80% April 23, 90% April 18. Observed last spring frost in recent years: 2021 May 11, 2022 April 28, 2023 April 29, 2024 April 21, 2025 April 29, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1May 15May 2Apr 182021: May 112022: April 282023: April 292024: April 212025: April 292026: May 20Fall at Alexandria: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% September 30, 30% October 3, 40% October 5, 50% October 8, 60% October 10, 70% October 14, 80% October 17, 90% October 20. Observed first fall frost in recent years: 2021 October 21, 2022 October 13, 2023 October 10, 2024 October 15.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 8Oct 202021: October 212022: October 132023: October 102024: October 15
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 21
2022April 28October 13
2023April 29October 10
2024April 21October 15
2025April 29incomplete record
2026May 20season not over yet

What these dates mean

September 27 is the cautious fall date for Alexandria, marking a 10 % chance that a light frost has arrived earlier, so finishing the harvest after this day carries the lowest risk for tender crops.

The median hard-frost dates are April 21 in spring and October 19 in fall; each signals a 50 % chance that a hard frost will occur later (spring) or earlier (fall) than the date, giving gardeners a sense of the central point of the hard-frost window. For tender crops the cautious spring date is May 15, which carries only a 10 % chance of a light frost later, while the cautious fall date remains September 27, with only a 10 % chance of a light frost earlier.

A hard frost at 28 °F can damage or kill plants that would survive a light frost at 32 °F, so it is the more consequential temperature threshold.

How to read the probabilities

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

  • Spring: "10% after May 15" 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 27" 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 Alexandria, MNNumbered nearest stations: 1 — Glenwood, MN — 15 mi; 2 — Long Prairie, MN — 25 mi; 3 — near Morris, MN — 30 mi; 4 — Benson, MN — 40 mi; 5 — Artichoke Lake 1 E, MN — 49 mi.SDND25 mi · 40 km1. Glenwood, MN — 15 mi12. Long Prairie, MN — 25 mi23. near Morris, MN — 30 mi34. Benson, MN — 40 mi45. Artichoke Lake 1 E, MN — 49 mi5
  1. Glenwood, MN 15 mi (24 km)
  2. Long Prairie, MN 25 mi (41 km)
  3. near Morris, MN 30 mi (48 km)
  4. Benson, MN 40 mi (64 km)
  5. Artichoke Lake 1 E, MN 49 mi (78 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: 45.8678, -95.3942.