U.S. Frost Dates by Weather Station

NOAA station USC00327530 · North Dakota

Frost Dates for Richardton Abbey, ND

NOAA weather station Richardton Abbey (USC00327530), North Dakota · elevation 2470 ft (753 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 23only 1 spring in 10 still has a frost later
  • Typical last frostMay 950% chance of a frost after it
  • Typical first fall frostOctober 150% chance of a frost before it
  • Frost-free season145 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Richardton Abbey, NDSpring: a frost after April 28 in 9 years out of 10, after May 9 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 1 in half of the years, before October 15 in 9 years out of 10. Typical frost-free season: 145 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Oct 1Frost season at Richardton Abbey, NDSpring: a frost after April 28 in 9 years out of 10, after May 9 in half of the years, after May 23 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before October 1 in half of the years, before October 15 in 9 years out of 10. Typical frost-free season: 145 days.JFMAMJJASONDLast frost ~May 9First frost ~Oct 1
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 23September 18
50% (typical)May 9October 1
90% (likely)April 28October 15
Frost-free season (32°F, 50% chance)
145 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 10

The last 15 years (2006–2020 normals)

Typical last frost May 11 (2 days later than the 30-year normal), typical first fall frost October 4 (3 days later). Frost-free season 145 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 Richardton Abbey: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 23, 20% May 19, 30% May 15, 40% May 12, 50% May 9, 60% May 7, 70% May 4, 80% May 1, 90% April 28. Observed last spring frost in recent years: 2024 May 4.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 23May 9Apr 282024: May 4Fall at Richardton Abbey: chance of a frost before this dateFall, chance of a frost before the date: 10% September 18, 20% September 24, 30% September 27, 40% September 29, 50% October 1, 60% October 4, 70% October 7, 80% October 10, 90% October 15. Observed first fall frost in recent years: 2021 October 15, 2022 October 7, 2024 October 15.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 18Oct 1Oct 152021: October 152022: October 72024: 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
2021no dataOctober 15
2022incomplete recordOctober 7
2023incomplete recordincomplete record
2024May 4October 15
2025incomplete recordincomplete record
2026incomplete recordseason not over yet

What these dates mean

The 145 days between the 50% dates in Richardton Abbey, May 9 and October 1, make up the period when a light frost (32 °F) is no more likely than not. Gardeners can treat this span as the primary window for planting and harvesting tender crops, knowing that a frost could still appear on either side of the interval.

For a cautious spring schedule, the late date of May 23 carries only a 10 % chance that a light frost will occur later, making it the preferred day to set out tender crops. In the fall, the early date of September 18 has only a 10 % chance that a light frost has already arrived, so it is the prudent day to finish harvesting those crops.

Hard frost dates—April 30 in spring and October 10 in fall—represent temperatures low enough to cause more severe damage than the 32 °F light frost, so they are a higher-risk threshold for sensitive plants.

How to read the probabilities

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

  • Spring: "10% after May 23" 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 18" 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 Richardton Abbey, NDNumbered nearest stations: 1 — Hebron, ND — 13 mi; 2 — near Dickinson, ND — 23 mi; 3 — Heart Butte Dam, ND — 32 mi; 4 — New England, ND — 35 mi; 5 — New Salem, ND — 39 mi.ND25 mi · 40 km1. Hebron, ND — 13 mi12. near Dickinson, ND — 23 mi23. Heart Butte Dam, ND — 32 mi34. New England, ND — 35 mi45. New Salem, ND — 39 mi5
  1. Hebron, ND 13 mi (21 km)
  2. near Dickinson, ND 23 mi (38 km)
  3. Heart Butte Dam, ND 32 mi (51 km)
  4. New England, ND 35 mi (57 km)
  5. New Salem, ND 39 mi (63 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: 46.8886, -102.3192.