U.S. Frost Dates by Weather Station

NOAA station USC00325730 · North Dakota

Frost Dates for McHenry, ND

NOAA weather station McHenry 3 W (USC00325730), North Dakota · elevation 1555 ft (474 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 25only 1 spring in 10 still has a frost later
  • Typical last frostMay 1250% chance of a frost after it
  • Typical first fall frostSeptember 2850% chance of a frost before it
  • Frost-free season139 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at McHenry, NDSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 25 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before September 28 in half of the years, before October 10 in 9 years out of 10. Typical frost-free season: 139 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 12First frost ~Sep 28Frost season at McHenry, NDSpring: a frost after April 30 in 9 years out of 10, after May 12 in half of the years, after May 25 in 1 year out of 10. Fall: the first frost comes before September 16 in 1 year out of 10, before September 28 in half of the years, before October 10 in 9 years out of 10. Typical frost-free season: 139 days.JFMAMJJASONDLast frost ~May 12First frost ~Sep 28
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.Today

Frost dates (32°F)

Probability of frost, based on 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 25September 16
50% (typical)May 12September 28
90% (likely)April 30October 10
Frost-free season (32°F, 50% chance)
139 days
Hard frost (28°F), last in spring, 50% chance after
May 3
Hard frost (28°F), first in fall, 50% chance before
October 7

The last 15 years (2006–2020 normals)

Typical last frost May 12 (same as the 30-year normal), typical first fall frost October 2 (4 days later). Frost-free season 142 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 McHenry: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 25, 20% May 20, 30% May 17, 40% May 15, 50% May 12, 60% May 10, 70% May 7, 80% May 4, 90% April 30. Observed last spring frost in recent years: 2021 May 11, 2022 May 21, 2023 May 2, 2024 May 25, 2025 April 29, 2026 May 20.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 25May 12Apr 302021: May 112022: May 212023: May 22024: May 252025: April 292026: May 20Fall at McHenry: chance of a frost before this dateFall, chance of a frost before the date: 10% September 16, 20% September 20, 30% September 23, 40% September 26, 50% September 28, 60% September 30, 70% October 2, 80% October 6, 90% October 10. Observed first fall frost in recent years: 2021 October 16, 2022 October 7, 2023 October 7, 2024 October 13, 2025 October 6.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 16Sep 28Oct 102021: October 162022: 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 11October 16
2022May 21October 7
2023May 2October 7
2024May 25October 13
2025April 29October 6
2026May 20season not over yet

What these dates mean

The 139-day span between the 32°F 50% dates in McHenry frames the period when the odds of a light frost are roughly even. The 32°F 50% dates are May 12 in spring and September 28 in fall, marking the median points of the frost-free window.

For tender crops, a cautious spring plan uses May 25, which carries only a 10 % chance of a frost occurring later, while planting on April 30 would face a 90 % chance and is a gamble. In fall, September 16 is the cautious date, with a 10 % chance that a frost has arrived earlier, whereas October 10 would be a gamble with a 90 % chance. The 28°F 50% dates are May 3 and October 7, and a hard frost at 28 °F can damage plant tissue that survives a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after May 25" 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 16" 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 McHenry, NDNumbered nearest stations: 1 — Petersburg, ND — 43 mi; 2 — Jamestown, ND — 45 mi; 3 — Jamestown State Hosp, ND — 48 mi; 4 — Harvey, ND — 59 mi; 5 — Streeter, ND — 71 mi.ND25 mi · 40 km1. Petersburg, ND — 43 mi12. Jamestown, ND — 45 mi23. Jamestown State Hosp, ND — 48 mi34. Harvey, ND — 59 mi45. Streeter, ND — 71 mi5
  1. Petersburg, ND 43 mi (69 km)
  2. Jamestown, ND 45 mi (73 km)
  3. Jamestown State Hosp, ND 48 mi (78 km)
  4. Harvey, ND 59 mi (96 km)
  5. Streeter, ND 71 mi (114 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: 47.5808, -98.6422.