U.S. Frost Dates by Weather Station

NOAA station USW00024012 · North Dakota

Frost Dates near Dickinson, ND

NOAA weather station Theodore Roosevelt Airport (USW00024012), North Dakota · elevation 2580 ft (786 m) · hardiness zone 4b*

Dickinson is the nearest town to the station (5.5 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter May 31only 1 spring in 10 still has a frost later
  • Typical last frostMay 1850% chance of a frost after it
  • Typical first fall frostSeptember 2550% chance of a frost before it
  • Frost-free season129 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season near Dickinson, NDSpring: a frost after May 6 in 9 years out of 10, after May 18 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 25 in half of the years, before October 7 in 9 years out of 10. Typical frost-free season: 129 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 18First frost ~Sep 25Frost season near Dickinson, NDSpring: a frost after May 6 in 9 years out of 10, after May 18 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 25 in half of the years, before October 7 in 9 years out of 10. Typical frost-free season: 129 days.JFMAMJJASONDLast frost ~May 18First frost ~Sep 25
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 31September 12
50% (typical)May 18September 25
90% (likely)May 6October 7
Frost-free season (32°F, 50% chance)
129 days
Hard frost (28°F), last in spring, 50% chance after
May 8
Hard frost (28°F), first in fall, 50% chance before
October 3

The last 15 years (2006–2020 normals)

Typical last frost May 18 (same as the 30-year normal), typical first fall frost September 28 (3 days later). Frost-free season 131 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 near Dickinson: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 31, 20% May 27, 30% May 24, 40% May 21, 50% May 18, 60% May 16, 70% May 13, 80% May 9, 90% May 6. Observed last spring frost in recent years: 2021 May 10, 2022 May 22, 2023 May 19, 2024 May 5, 2025 May 22, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 31May 18May 62021: May 102022: May 222023: May 192024: May 52025: May 222026: May 7Fall near Dickinson: chance of a frost before this dateFall, chance of a frost before the date: 10% September 12, 20% September 17, 30% September 20, 40% September 22, 50% September 25, 60% September 27, 70% September 30, 80% October 3, 90% October 7. Observed first fall frost in recent years: 2021 October 15, 2022 October 6, 2023 October 6, 2024 September 22, 2025 September 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 12Sep 25Oct 72021: October 152022: October 62023: October 62024: September 222025: September 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 10October 15
2022May 22October 6
2023May 19October 6
2024May 5September 22
2025May 22September 6
2026May 7season not over yet

What these dates mean

The 129 days between the 50% dates in the Dickinson area mark the window in which the likelihood of a light frost is roughly even. The 50% light-frost dates are May 18 in spring and September 25 in fall; a gardener can treat them as reference points for balanced risk, while the 50% hard-frost dates are May 8 and October 3, indicating when a 28 °F frost is equally probable.

To minimize risk, a cautious plan for tender crops in spring follows the May 31 date, which carries only a 10 % chance of a later frost, whereas in fall the cautious date is September 12, with only a 10 % chance that frost has arrived earlier. Planting on May 6 or keeping crops until October 7 would be a gamble, each bearing a 90 % chance of frost before or after the respective date.

A hard frost at 28 °F can damage plants that survive a light frost at 32 °F, so it is a more critical threshold for tender crops.

How to read the probabilities

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

  • Spring: "10% after May 31" 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 12" 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 Dickinson, NDNumbered nearest stations: 1 — New England, ND — 18 mi; 2 — Richardton Abbey, ND — 23 mi; 3 — Medora, ND — 35 mi; 4 — Hebron, ND — 37 mi; 5 — Grassy Butte, ND — 46 mi.NDMT25 mi · 40 km1. New England, ND — 18 mi12. Richardton Abbey, ND — 23 mi23. Medora, ND — 35 mi34. Hebron, ND — 37 mi45. Grassy Butte, ND — 46 mi5
  1. New England, ND 18 mi (29 km)
  2. Richardton Abbey, ND 23 mi (38 km)
  3. Medora, ND 35 mi (57 km)
  4. Hebron, ND 37 mi (59 km)
  5. Grassy Butte, ND 46 mi (74 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: 46.7994, -102.7972.