U.S. Frost Dates by Weather Station

NOAA station USC00211063 · Minnesota

Frost Dates for Browns Valley, MN

NOAA weather station Browns Valley (USC00211063), Minnesota · elevation 978 ft (298 m) · hardiness zone 4b*

  • Lower-risk planting dateafter May 22only 1 spring in 10 still has a frost later
  • Typical last frostMay 950% chance of a frost after it
  • Typical first fall frostSeptember 2850% chance of a frost before it
  • Frost-free season141 daystypical year, 32°F
  • Hardiness zone4bcalculated*

The year at a glance

Frost season at Browns Valley, MNSpring: a frost after April 28 in 9 years out of 10, after May 9 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 15 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: 141 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 9First frost ~Sep 28Frost season at Browns Valley, MNSpring: a frost after April 28 in 9 years out of 10, after May 9 in half of the years, after May 22 in 1 year out of 10. Fall: the first frost comes before September 15 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: 141 days.JFMAMJJASONDLast frost ~May 9First 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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 22September 15
50% (typical)May 9September 28
90% (likely)April 28October 10
Frost-free season (32°F, 50% chance)
141 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 8 (1 day earlier than the 30-year normal), typical first fall frost September 30 (2 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 Browns Valley: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 22, 20% May 17, 30% May 15, 40% May 12, 50% May 9, 60% May 6, 70% May 4, 80% May 1, 90% April 28. Observed last spring frost in recent years: 2021 May 29, 2022 April 29, 2023 May 4.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 22May 9Apr 282021: May 292022: April 292023: May 4Fall at Browns Valley: 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 25, 50% September 28, 60% September 30, 70% October 2, 80% October 6, 90% October 10. Observed first fall frost in recent years: 2021 October 21, 2022 September 28.Fall: first frostChance of a frost before this date10%50%90%Sep 1Oct 1Sep 15Sep 28Oct 102021: October 212022: September 28
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 29September 28
2023May 4incomplete record
2024incomplete recordno data
2025no datano data
2026no dataseason not over yet

What these dates mean

May 22 is the cautious spring light-frost date for Browns Valley; with only a 10% chance of a frost later, a gardener can plan to set out tender crops on that day.

The 50% date is May 9, indicating an even chance of a light frost occurring later in spring, while the 50% date is September 28, indicating an even chance of a light frost occurring earlier in fall. The hard-frost 50% dates are April 30 and October 7; a 28°F frost can injure or kill plants that would survive a 32°F light frost, so it is a more severe threat.

September 15 is the cautious fall light-frost date, with only a 10% chance that a frost has arrived earlier, allowing a gardener to finish harvesting tender crops with minimal risk.

How to read the probabilities

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

  • Spring: "10% after May 22" 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 Browns Valley, MNNumbered nearest stations: 1 — Sisseton, SD — 11 mi; 2 — Wheaton, MN — 21 mi; 3 — Victor, SD — 22 mi; 4 — Summit, SD — 23 mi; 5 — Waubay National Wild Life, SD — 27 mi.SDMNND25 mi · 40 km1. Sisseton, SD — 11 mi12. Wheaton, MN — 21 mi23. Victor, SD — 22 mi34. Summit, SD — 23 mi45. Waubay National Wild Life, SD — 27 mi5
  1. Sisseton, SD 11 mi (18 km)
  2. Wheaton, MN 21 mi (35 km)
  3. Victor, SD 22 mi (36 km)
  4. Summit, SD 23 mi (37 km)
  5. Waubay National Wild Life, SD 27 mi (43 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: 45.5958, -96.8283.