U.S. Frost Dates by Weather Station

NOAA station USC00328840 · North Dakota

Frost Dates for Turtle Lake, ND

NOAA weather station Turtle Lake (USC00328840), North Dakota · elevation 1893 ft (577 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 26only 1 spring in 10 still has a frost later
  • Typical last frostMay 1450% chance of a frost after it
  • Typical first fall frostSeptember 2650% chance of a frost before it
  • Frost-free season136 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Turtle Lake, NDSpring: a frost after May 3 in 9 years out of 10, after May 14 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 26 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 136 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 14First frost ~Sep 26Frost season at Turtle Lake, NDSpring: a frost after May 3 in 9 years out of 10, after May 14 in half of the years, after May 26 in 1 year out of 10. Fall: the first frost comes before September 15 in 1 year out of 10, before September 26 in half of the years, before October 9 in 9 years out of 10. Typical frost-free season: 136 days.JFMAMJJASONDLast frost ~May 14First frost ~Sep 26
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 26September 15
50% (typical)May 14September 26
90% (likely)May 3October 9
Frost-free season (32°F, 50% chance)
136 days
Hard frost (28°F), last in spring, 50% chance after
May 5
Hard frost (28°F), first in fall, 50% chance before
October 5

The last 15 years (2006–2020 normals)

Typical last frost May 13 (1 day earlier than the 30-year normal), typical first fall frost October 2 (6 days later). Frost-free season 141 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 Turtle Lake: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 26, 20% May 22, 30% May 19, 40% May 17, 50% May 14, 60% May 12, 70% May 10, 80% May 7, 90% May 3. Observed last spring frost in recent years: 2021 May 12, 2022 May 5, 2023 May 3, 2024 May 1, 2025 April 30, 2026 May 10.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 26May 14May 32021: May 122022: May 52023: May 32024: May 12025: April 302026: May 10Fall at Turtle Lake: chance of a frost before this dateFall, chance of a frost before the date: 10% September 15, 20% September 19, 30% September 22, 40% September 24, 50% September 26, 60% September 28, 70% October 1, 80% October 4, 90% October 9. Observed first fall frost in recent years: 2021 October 20, 2022 October 7, 2023 October 7, 2024 October 13, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 15Sep 26Oct 92021: October 202022: October 72023: October 72024: October 132025: 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 12October 20
2022May 5October 7
2023May 3October 7
2024May 1October 13
2025April 30October 6
2026May 10season not over yet

What these dates mean

September 15 is the cautious fall date for finishing the harvest of tender crops in Turtle Lake, since there is only a 10 % chance that a light frost has arrived earlier. For a similarly low risk in spring, the cautious date to set out tender crops is May 26, when the chance of a later light frost is just 10 %.

The 50 % dates mark the point at which the odds of a light frost are even: May 14 in spring and September 26 in fall. Gardeners can treat those dates as a midpoint of frost risk, with earlier or later plantings carrying higher probabilities of frost. A hard frost at 28 °F can injure or kill plants more severely than a light frost at 32 °F. The hard-frost 50 % dates are May 5 in spring and October 5 in fall, providing a reference for the colder freeze threshold.

How to read the probabilities

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

  • Spring: "10% after May 26" 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 15" 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 Turtle Lake, NDNumbered nearest stations: 1 — Underwood, ND — 13 mi; 2 — McClusky, ND — 21 mi; 3 — Garrison, ND — 26 mi; 4 — Max, ND — 28 mi; 5 — Drake, ND — 45 mi.ND25 mi · 40 km1. Underwood, ND — 13 mi12. McClusky, ND — 21 mi23. Garrison, ND — 26 mi34. Max, ND — 28 mi45. Drake, ND — 45 mi5
  1. Underwood, ND 13 mi (21 km)
  2. McClusky, ND 21 mi (34 km)
  3. Garrison, ND 26 mi (42 km)
  4. Max, ND 28 mi (45 km)
  5. Drake, ND 45 mi (73 km)

Sources

* Hardiness zone 4a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 47.5214, -100.8883.