U.S. Frost Dates by Weather Station

NOAA station USC00320995 · North Dakota

Frost Dates for Bowman, ND

NOAA weather station Bowman (USC00320995), North Dakota · elevation 2983 ft (909 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 29only 1 spring in 10 still has a frost later
  • Typical last frostMay 1650% chance of a frost after it
  • Typical first fall frostSeptember 2550% chance of a frost before it
  • Frost-free season132 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Bowman, NDSpring: a frost after May 5 in 9 years out of 10, after May 16 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before September 11 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: 132 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 16First frost ~Sep 25Frost season at Bowman, NDSpring: a frost after May 5 in 9 years out of 10, after May 16 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before September 11 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: 132 days.JFMAMJJASONDLast frost ~May 16First 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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 29September 11
50% (typical)May 16September 25
90% (likely)May 5October 7
Frost-free season (32°F, 50% chance)
132 days
Hard frost (28°F), last in spring, 50% chance after
May 5
Hard frost (28°F), first in fall, 50% chance before
October 3

The last 15 years (2006–2020 normals)

Typical last frost May 15 (1 day earlier than the 30-year normal), typical first fall frost September 29 (4 days later). Frost-free season 137 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 Bowman: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 29, 20% May 24, 30% May 21, 40% May 18, 50% May 16, 60% May 14, 70% May 11, 80% May 9, 90% May 5. Observed last spring frost in recent years: 2021 May 27, 2022 May 22, 2023 May 2, 2024 May 5, 2025 May 22, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 29May 16May 52021: May 272022: May 222023: May 22024: May 52025: May 222026: May 7Fall at Bowman: chance of a frost before this dateFall, chance of a frost before the date: 10% September 11, 20% September 17, 30% September 20, 40% September 23, 50% September 25, 60% September 28, 70% September 30, 80% October 3, 90% October 7. Observed first fall frost in recent years: 2021 October 13, 2022 October 7, 2023 October 6, 2024 October 1, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 11Sep 25Oct 72021: October 132022: October 72023: October 62024: October 12025: 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 27October 13
2022May 22October 7
2023May 2October 6
2024May 5October 1
2025May 22October 6
2026May 7season not over yet

What these dates mean

September 11 marks the cautious fall date in Bowman, carrying only a 10 % chance that a light frost has arrived, so it is the date to aim for when finishing the harvest of tender crops.

In spring the cautious date for setting out tender crops is May 29, which has a 10 % chance of a frost later; the gamble date is May 5 with a 90 % chance. The 50% light-frost dates are May 16, meaning there is a 50 % chance of a frost later than this date, and September 25, meaning there is a 50 % chance of a frost earlier than this date. The 50% hard-frost dates are May 5 and October 3.

Hard frost at 28 °F can injure plant tissue that typically survives a light frost at 32 °F, making it the 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 29" 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 11" 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 Bowman, NDNumbered nearest stations: 1 — New England, ND — 34 mi; 2 — near Dickinson, ND — 50 mi; 3 — Medora, ND — 50 mi; 4 — Camp Crook, SD — 53 mi; 5 — Plevna, MT — 57 mi.MTSD25 mi · 40 km1. New England, ND — 34 mi12. near Dickinson, ND — 50 mi23. Medora, ND — 50 mi34. Camp Crook, SD — 53 mi45. Plevna, MT — 57 mi5
  1. New England, ND 34 mi (55 km)
  2. near Dickinson, ND 50 mi (80 km)
  3. Medora, ND 50 mi (81 km)
  4. Camp Crook, SD 53 mi (86 km)
  5. Plevna, MT 57 mi (91 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: 46.1936, -103.3714.