U.S. Frost Dates by Weather Station

NOAA station USC00324418 · North Dakota

Frost Dates for Jamestown State Hosp, ND

NOAA weather station Jamestown State Hosp (USC00324418), North Dakota · elevation 1467 ft (447 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 21only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostSeptember 2950% chance of a frost before it
  • Frost-free season143 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Jamestown State Hosp, NDSpring: a frost after April 26 in 9 years out of 10, after May 8 in half of the years, after May 21 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: 143 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Sep 29Frost season at Jamestown State Hosp, NDSpring: a frost after April 26 in 9 years out of 10, after May 8 in half of the years, after May 21 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: 143 days.JFMAMJJASONDLast frost ~May 8First 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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 21September 17
50% (typical)May 8September 29
90% (likely)April 26October 11
Frost-free season (32°F, 50% chance)
143 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 7

The last 15 years (2006–2020 normals)

Typical last frost May 7 (1 day earlier than the 30-year normal), typical first fall frost October 5 (6 days later). Frost-free season 149 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 Jamestown State Hosp: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 21, 20% May 16, 30% May 13, 40% May 11, 50% May 8, 60% May 6, 70% May 3, 80% April 30, 90% April 26. Observed last spring frost in recent years: 2021 May 29, 2022 April 29, 2023 May 3, 2024 May 1, 2025 April 30, 2026 May 8.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 21May 8Apr 262021: May 292022: April 292023: May 32024: May 12025: April 302026: May 8Fall at Jamestown State Hosp: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 21, 30% September 25, 40% September 27, 50% September 29, 60% October 1, 70% October 3, 80% October 6, 90% October 11. Observed first fall frost in recent years: 2021 October 21, 2022 October 7, 2023 October 7, 2024 October 15, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Sep 29Oct 112021: October 212022: October 72023: October 72024: October 152025: October 22
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 29October 21
2022April 29October 7
2023May 3October 7
2024May 1October 15
2025April 30October 22
2026May 8season not over yet

What these dates mean

The 143 days between the 50% dates in Jamestown State Hosp, May 8 and September 29, mark the interval when a light frost (32 °F) is less likely than not for a gardener. Within this window the risk of a frost drops below 50 %, giving a clearer span for planting and harvesting activities.

In spring the cautious date for setting out tender crops is May 21, when there is only a 10 % chance of a frost later; planting on April 26 would involve a 90 % chance and is a gamble. In fall the cautious date to finish harvesting tender crops is September 17, with a 10 % chance of a frost earlier, while waiting until October 11 carries a 90 % chance and is risky. The hard-frost median dates are April 30 and October 7, and a hard frost can damage plants more severely than a light frost because it reaches lower temperatures.

How to read the probabilities

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

  • Spring: "10% after May 21" 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 Jamestown State Hosp, NDNumbered nearest stations: 1 — Jamestown, ND — 3 mi; 2 — Streeter, ND — 38 mi; 3 — McHenry, ND — 48 mi; 4 — Fullerton, ND — 52 mi; 5 — Napoleon, ND — 58 mi.ND25 mi · 40 km1. Jamestown, ND — 3 mi12. Streeter, ND — 38 mi23. McHenry, ND — 48 mi34. Fullerton, ND — 52 mi45. Napoleon, ND — 58 mi5
  1. Jamestown, ND 3 mi (5 km)
  2. Streeter, ND 38 mi (61 km)
  3. McHenry, ND 48 mi (78 km)
  4. Fullerton, ND 52 mi (84 km)
  5. Napoleon, ND 58 mi (93 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: 46.8844, -98.685.