U.S. Frost Dates by Weather Station

NOAA station USC00323376 · North Dakota

Frost Dates for Garrison, ND

NOAA weather station Garrison (USC00323376), North Dakota · elevation 1932 ft (589 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 24only 1 spring in 10 still has a frost later
  • Typical last frostMay 1250% chance of a frost after it
  • Typical first fall frostSeptember 3050% chance of a frost before it
  • Frost-free season140 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Garrison, NDSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 24 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: 140 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 12First frost ~Sep 30Frost season at Garrison, NDSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 24 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: 140 days.JFMAMJJASONDLast frost ~May 12First 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.Today

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 24September 17
50% (typical)May 12September 30
90% (likely)April 30October 12
Frost-free season (32°F, 50% chance)
140 days
Hard frost (28°F), last in spring, 50% chance after
May 2
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 11 (1 day earlier than the 30-year normal), typical first fall frost October 3 (3 days later). Frost-free season 143 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 Garrison: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 24, 20% May 20, 30% May 17, 40% May 15, 50% May 12, 60% May 9, 70% May 7, 80% May 4, 90% April 30. Observed last spring frost in recent years: 2021 May 11, 2022 May 21, 2023 May 2, 2024 May 1, 2025 May 17, 2026 May 10.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 24May 12Apr 302021: May 112022: May 212023: May 22024: May 12025: May 172026: May 10Fall at Garrison: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 22, 30% September 24, 40% September 27, 50% September 30, 60% October 2, 70% October 5, 80% October 7, 90% October 12. Observed first fall frost in recent years: 2021 October 20, 2022 October 7, 2023 October 7, 2024 October 12, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Sep 30Oct 122021: October 202022: October 72023: October 72024: October 122025: October 6
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 20
2022May 21October 7
2023May 2October 7
2024May 1October 12
2025May 17October 6
2026May 10season not over yet

What these dates mean

Setting out tender crops on April 30 in Garrison is a gamble, as there is a 90% chance of a frost later than that date. Gardeners who prefer a lower risk wait until the cautious spring date of May 24, when only a 10% chance of a later frost remains.

The 50% date is May 12; this marks the point at which a frost is equally likely to occur later. In the fall, the cautious date to finish harvesting tender crops is September 17, carrying a 10% chance that a frost has arrived earlier. The 50% date is September 30, indicating an even chance of a frost earlier. Hard-frost thresholds are given by the 28°F dates, May 2 and October 8, and a hard frost can injure plants that survive a light frost. The record spans 28 years, and the interval between the two 32°F 50% dates is 140 days.

How to read the probabilities

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

  • Spring: "10% after May 24" 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 Garrison, NDNumbered nearest stations: 1 — Max, ND — 13 mi; 2 — Underwood, ND — 19 mi; 3 — Turtle Lake, ND — 26 mi; 4 — near Minot, ND — 37 mi; 5 — Minot (Airport), ND — 42 mi.25 mi · 40 km1. Max, ND — 13 mi12. Underwood, ND — 19 mi23. Turtle Lake, ND — 26 mi34. near Minot, ND — 37 mi45. Minot (Airport), ND — 42 mi5
  1. Max, ND 13 mi (21 km)
  2. Underwood, ND 19 mi (30 km)
  3. Turtle Lake, ND 26 mi (42 km)
  4. near Minot, ND 37 mi (59 km)
  5. Minot (Airport), ND 42 mi (68 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: 47.6539, -101.4197.