U.S. Frost Dates by Weather Station

NOAA station USC00217502 · Minnesota

Frost Dates for Santiago, MN

NOAA weather station Santiago 3 E (USC00217502), Minnesota · elevation 1010 ft (308 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 22only 1 spring in 10 still has a frost later
  • Typical last frostMay 750% chance of a frost after it
  • Typical first fall frostSeptember 2850% chance of a frost before it
  • Frost-free season144 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Santiago, MNSpring: a frost after April 24 in 9 years out of 10, after May 7 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 28 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 144 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 7First frost ~Sep 28Frost season at Santiago, MNSpring: a frost after April 24 in 9 years out of 10, after May 7 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 28 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 144 days.JFMAMJJASONDLast frost ~May 7First frost ~Sep 28
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.Today

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 22September 15
50% (typical)May 7September 28
90% (likely)April 24October 11
Frost-free season (32°F, 50% chance)
144 days
Hard frost (28°F), last in spring, 50% chance after
April 28
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 4 (3 days earlier than the 30-year normal), typical first fall frost October 1 (3 days later). Frost-free season 146 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 Santiago: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 22, 20% May 17, 30% May 13, 40% May 10, 50% May 7, 60% May 3, 70% May 1, 80% April 28, 90% April 24. Observed last spring frost in recent years: 2021 May 29, 2022 April 28, 2023 May 3, 2024 April 24, 2025 May 3, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 22May 7Apr 242021: May 292022: April 282023: May 32024: April 242025: May 32026: May 20Fall at Santiago: chance of a frost before this dateFall, chance of a frost before the date: 10% September 15, 20% September 20, 30% September 23, 40% September 26, 50% September 28, 60% October 1, 70% October 4, 80% October 7, 90% October 11. Observed first fall frost in recent years: 2021 October 17, 2022 September 28, 2023 October 9, 2024 October 4, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 15Sep 28Oct 112021: October 172022: 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 29October 17
2022April 28September 28
2023May 3October 9
2024April 24October 4
2025May 3October 8
2026May 20season not over yet

What these dates mean

The cautious fall date for finishing the harvest in Santiago is September 15, when there is only a 10 % chance that a light frost has arrived. Gardeners who wait beyond this point run a much higher risk of frost damage to tender crops.

The 50 % light-frost dates are May 7 in spring and September 28 in fall; on each of those days a gardener faces an even chance of a frost occurring later (spring) or earlier (fall). The median hard-frost dates are April 28 and October 8, marking the point at which a 28 °F frost is as likely as not.

For a cautious plan, tender crops are set out after the spring cautious date of May 22, which carries only a 10 % chance of a later frost, and are harvested by the fall cautious date of September 15. A hard frost at 28 °F can damage plant tissue that survives a light frost at 32 °F, so it represents a higher risk.

How to read the probabilities

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

  • Spring: "10% after May 22" 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 15" 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 Santiago, MNNumbered nearest stations: 1 — Saint Cloud, MN — 14 mi; 2 — near Collegeville, MN — 31 mi; 3 — Mora, MN — 31 mi; 4 — New Hope, MN — 41 mi; 5 — Forest Lake, MN — 44 mi.WI25 mi · 40 km1. Saint Cloud, MN — 14 mi12. near Collegeville, MN — 31 mi23. Mora, MN — 31 mi34. New Hope, MN — 41 mi45. Forest Lake, MN — 44 mi5
  1. Saint Cloud, MN 14 mi (23 km)
  2. near Collegeville, MN 31 mi (50 km)
  3. Mora, MN 31 mi (50 km)
  4. New Hope, MN 41 mi (67 km)
  5. Forest Lake, MN 44 mi (71 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: 45.5458, -93.7572.