U.S. Frost Dates by Weather Station

NOAA station USC00328366 · North Dakota

Frost Dates for Steele, ND

NOAA weather station Steele 4 N (USC00328366), North Dakota · elevation 1853 ft (565 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 28only 1 spring in 10 still has a frost later
  • Typical last frostMay 1550% chance of a frost after it
  • Typical first fall frostSeptember 2550% chance of a frost before it
  • Frost-free season133 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Steele, NDSpring: a frost after May 4 in 9 years out of 10, after May 15 in half of the years, after May 28 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 133 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 15First frost ~Sep 25Frost season at Steele, NDSpring: a frost after May 4 in 9 years out of 10, after May 15 in half of the years, after May 28 in 1 year out of 10. Fall: the first frost comes before September 12 in 1 year out of 10, before September 25 in half of the years, before October 8 in 9 years out of 10. Typical frost-free season: 133 days.JFMAMJJASONDLast frost ~May 15First 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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 28September 12
50% (typical)May 15September 25
90% (likely)May 4October 8
Frost-free season (32°F, 50% chance)
133 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 15 (same as the 30-year normal), typical first fall frost September 28 (3 days later). Frost-free season 134 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 Steele: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 28, 20% May 24, 30% May 20, 40% May 17, 50% May 15, 60% May 12, 70% May 10, 80% May 7, 90% May 4.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 28May 15May 4Fall at Steele: chance of a frost before this dateFall, chance of a frost before the date: 10% September 12, 20% September 18, 30% September 20, 40% September 23, 50% September 25, 60% September 28, 70% September 30, 80% October 3, 90% October 8.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 12Sep 25Oct 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.

What these dates mean

May 28 is the cautious spring light-frost date, giving a gardener only a 10 % chance of a frost occurring later and therefore marking a reliable point to set out tender crops.

The 50 % light-frost dates are May 15 and September 25; at each of these dates a gardener faces an even chance of a frost later in spring or earlier in fall. For a risk-averse plan the cautious dates are May 28 for planting and September 12 for finishing harvest of tender crops, while May 4 and October 8 represent high-risk gambles.

Hard-frost risk is shown by the 50 % dates May 5 and October 5, and a hard frost at 28 °F can damage plants more severely than a light frost at 32 °F. The 26-year record underlies these probabilities for Steele.

How to read the probabilities

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

  • Spring: "10% after May 28" 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 12" 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 Steele, NDNumbered nearest stations: 1 — Streeter, ND — 27 mi; 2 — Napoleon, ND — 28 mi; 3 — Hazelton, ND — 32 mi; 4 — Bismarck, ND — 39 mi; 5 — Mandan, ND — 46 mi.ND25 mi · 40 km1. Streeter, ND — 27 mi12. Napoleon, ND — 28 mi23. Hazelton, ND — 32 mi34. Bismarck, ND — 39 mi45. Mandan, ND — 46 mi5
  1. Streeter, ND 27 mi (43 km)
  2. Napoleon, ND 28 mi (45 km)
  3. Hazelton, ND 32 mi (52 km)
  4. Bismarck, ND 39 mi (63 km)
  5. Mandan, ND 46 mi (74 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: 46.8947, -99.9483.