U.S. Frost Dates by Weather Station

NOAA station USC00420928 · Utah

Frost Dates for Brigham City, UT

NOAA weather station Brigham City Waste Plant (USC00420928), Utah · elevation 4240 ft (1292 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 29only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 550% chance of a frost before it
  • Frost-free season150 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Brigham City, UTSpring: a frost after April 20 in 9 years out of 10, after May 5 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 5 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 150 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 5Frost season at Brigham City, UTSpring: a frost after April 20 in 9 years out of 10, after May 5 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 5 in half of the years, before October 19 in 9 years out of 10. Typical frost-free season: 150 days.JFMAMJJASONDLast frost ~May 5First frost ~Oct 5
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 29September 20
50% (typical)May 5October 5
90% (likely)April 20October 19
Frost-free season (32°F, 50% chance)
150 days
Hard frost (28°F), last in spring, 50% chance after
April 18
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 2 (3 days earlier than the 30-year normal), typical first fall frost October 10 (5 days later). Frost-free season 157 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 Brigham City: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 29, 20% May 19, 30% May 14, 40% May 9, 50% May 5, 60% May 2, 70% April 29, 80% April 26, 90% April 20. Observed last spring frost in recent years: 2021 May 11, 2022 May 23, 2023 April 26, 2024 May 8, 2025 April 19, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 29May 5Apr 202021: May 112022: May 232023: April 262024: May 82025: April 192026: May 19Fall at Brigham City: chance of a frost before this dateFall, chance of a frost before the date: 10% September 20, 20% September 26, 30% September 29, 40% October 2, 50% October 5, 60% October 7, 70% October 10, 80% October 15, 90% October 19. Observed first fall frost in recent years: 2021 September 30, 2022 October 24, 2023 October 27, 2024 October 25, 2025 October 21.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 20Oct 5Oct 192021: September 302022: October 242023: October 272024: October 252025: October 21
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 11September 30
2022May 23October 24
2023April 26October 27
2024May 8October 25
2025April 19October 21
2026May 19season not over yet

What these dates mean

May 29 is the cautious spring date for Brigham City, and with only a 10 % chance of a light frost after that day a gardener can plan to set out tender crops.

The 50% date is May 5, meaning there is a 50 % chance of a light frost later than this date, while the 50% date in fall is October 5, meaning there is a 50 % chance of a light frost earlier than this date. The cautious fall date is September 20, when there is only a 10 % chance that a light frost has arrived, allowing gardeners to finish harvesting tender crops. The 50% hard-frost dates are April 18 in spring and October 17 in fall; these are the points where a hard frost at 28 °F is equally likely to have occurred or not. A hard frost matters more because temperatures of 28 °F can damage plants that survive 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 29" 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 20" 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 Brigham City, UTNumbered nearest stations: 1 — Logan Radio Kvnu, UT — 17 mi; 2 — near Logan, UT — 20 mi; 3 — near Ogden, UT — 21 mi; 4 — near Garland, UT — 21 mi; 5 — Richmond, UT — 29 mi.UTWYID25 mi · 40 km1. Logan Radio Kvnu, UT — 17 mi12. near Logan, UT — 20 mi23. near Ogden, UT — 21 mi34. near Garland, UT — 21 mi45. Richmond, UT — 29 mi5
  1. Logan Radio Kvnu, UT 17 mi (28 km)
  2. near Logan, UT 20 mi (32 km)
  3. near Ogden, UT 21 mi (34 km)
  4. near Garland, UT 21 mi (34 km)
  5. Richmond, UT 29 mi (47 km)

Sources

* Hardiness zone 6b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.5242, -112.0436.