U.S. Frost Dates by Weather Station

NOAA station USW00014924 · North Dakota

Frost Dates for Pembina, ND

NOAA weather station Pembina (USW00014924), North Dakota · elevation 790 ft (241 m) · hardiness zone 3b*

  • Lower-risk planting dateafter May 31only 1 spring in 10 still has a frost later
  • Typical last frostMay 1650% chance of a frost after it
  • Typical first fall frostSeptember 2950% chance of a frost before it
  • Frost-free season137 daystypical year, 32°F
  • Hardiness zone3bcalculated*

The year at a glance

Frost season at Pembina, NDSpring: a frost after May 2 in 9 years out of 10, after May 16 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 137 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 16First frost ~Sep 29Frost season at Pembina, NDSpring: a frost after May 2 in 9 years out of 10, after May 16 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before September 29 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 137 days.JFMAMJJASONDLast frost ~May 16First frost ~Sep 29
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 31September 17
50% (typical)May 16September 29
90% (likely)May 2October 11
Frost-free season (32°F, 50% chance)
137 days
Hard frost (28°F), last in spring, 50% chance after
May 5
Hard frost (28°F), first in fall, 50% chance before
October 7

The last 15 years (2006–2020 normals)

Typical last frost May 14 (2 days earlier than the 30-year normal), typical first fall frost October 2 (3 days later). Frost-free season 139 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 Pembina: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 31, 20% May 25, 30% May 21, 40% May 18, 50% May 16, 60% May 13, 70% May 9, 80% May 5, 90% May 2. Observed last spring frost in recent years: 2021 May 10, 2022 May 4, 2023 May 19, 2024 April 29, 2025 May 3, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 31May 16May 22021: May 102022: May 42023: May 192024: April 292025: May 32026: May 20Fall at Pembina: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 21, 30% September 24, 40% September 27, 50% September 29, 60% October 1, 70% October 4, 80% October 6, 90% October 11. Observed first fall frost in recent years: 2021 October 20, 2022 September 28, 2023 October 8, 2024 October 15, 2025 October 8.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Sep 29Oct 112021: October 202022: September 282023: October 82024: October 152025: 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 10October 20
2022May 4September 28
2023May 19October 8
2024April 29October 15
2025May 3October 8
2026May 20season not over yet

What these dates mean

The 137 days between the 50% dates in Pembina, May 16 and September 29, mark the interval framed by equal odds of a light frost at either end.

For a gardener, the 50% dates represent the median points where a light frost is just as likely as not, giving a balanced reference for timing. The cautious spring date is May 31, when there is only a 10 % chance of a light frost later; planting tender crops after that reduces risk. In fall, the cautious date is September 17, with only a 10 % chance that a light frost has arrived earlier, so finishing tender harvests by then is lower risk.

A hard frost at 28 °F is more damaging than a light frost at 32 °F because the lower temperature can injure plant tissue that survives milder frosts.

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 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 Pembina, NDNumbered nearest stations: 1 — Cavalier, ND — 22 mi; 2 — Argyle, MN — 48 mi; 3 — Grand Forks (Airport), ND — 71 mi; 4 — near Grand Forks, ND — 73 mi; 5 — Petersburg, ND — 74 mi.NDMN25 mi · 40 km1. Cavalier, ND — 22 mi12. Argyle, MN — 48 mi23. Grand Forks (Airport), ND — 71 mi34. near Grand Forks, ND — 73 mi45. Petersburg, ND — 74 mi5
  1. Cavalier, ND 22 mi (36 km)
  2. Argyle, MN 48 mi (77 km)
  3. Grand Forks (Airport), ND 71 mi (114 km)
  4. near Grand Forks, ND 73 mi (117 km)
  5. Petersburg, ND 74 mi (118 km)

Sources

* Hardiness zone 3b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 48.9711, -97.2417.