U.S. Frost Dates by Weather Station

NOAA station USC00352997 · Oregon

Frost Dates for Forest Grove, OR

NOAA weather station Forest Grove (USC00352997), Oregon · elevation 180 ft (55 m) · hardiness zone 8b*

  • Lower-risk planting dateafter May 5only 1 spring in 10 still has a frost later
  • Typical last frostApril 1650% chance of a frost after it
  • Typical first fall frostOctober 2650% chance of a frost before it
  • Frost-free season192 daystypical year, 32°F
  • Hardiness zone8bcalculated*

The year at a glance

Frost season at Forest Grove, ORSpring: a frost after March 26 in 9 years out of 10, after April 16 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 26 in half of the years, before November 14 in 9 years out of 10. Typical frost-free season: 192 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 16First frost ~Oct 26Frost season at Forest Grove, ORSpring: a frost after March 26 in 9 years out of 10, after April 16 in half of the years, after May 5 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 26 in half of the years, before November 14 in 9 years out of 10. Typical frost-free season: 192 days.JFMAMJJASONDLast frost ~Apr 16First frost ~Oct 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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 5October 6
50% (typical)April 16October 26
90% (likely)March 26November 14
Frost-free season (32°F, 50% chance)
192 days
Hard frost (28°F), last in spring, 50% chance after
March 19
Hard frost (28°F), first in fall, 50% chance before
November 11

The last 15 years (2006–2020 normals)

Typical last frost April 17 (1 day later than the 30-year normal), typical first fall frost October 25 (1 day earlier). Frost-free season 191 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 Forest Grove: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 5, 20% April 30, 30% April 26, 40% April 20, 50% April 16, 60% April 11, 70% April 6, 80% April 1, 90% March 26. Observed last spring frost in recent years: 2021 April 12, 2022 May 13, 2023 April 20, 2024 March 7, 2025 March 18, 2026 April 16.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1May 1May 5Apr 16Mar 262021: April 122022: May 132023: April 202024: March 72025: March 182026: April 16Fall at Forest Grove: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 13, 30% October 18, 40% October 22, 50% October 26, 60% October 30, 70% November 3, 80% November 7, 90% November 14. Observed first fall frost in recent years: 2021 October 12, 2022 November 9, 2023 October 28, 2024 November 15, 2025 November 30.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Dec 1Oct 6Oct 26Nov 142021: October 122022: November 92023: October 282024: November 152025: November 30
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
2021April 12October 12
2022May 13November 9
2023April 20October 28
2024March 7November 15
2025March 18November 30
2026April 16season not over yet

What these dates mean

May 5 is the cautious spring date, with only a 10 % chance that a light frost will occur later, and it lets a gardener set out tender crops. The median 32°F date in spring is April 16; at that point there is a 50 % chance of a light frost later, so the risk is evenly split. In fall the median 32°F date is October 26, meaning a 50 % chance of a light frost earlier, giving a clear midpoint for planning. October 6 is the cautious fall date, carrying a 10 % chance that a light frost has already arrived, and it marks the date by which tender crops should be finished harvesting. The hard-frost 50 % dates are March 19 in spring and November 11 in fall; a hard frost can damage plants more severely than a light frost, so those dates are especially important for growers.

How to read the probabilities

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

  • Spring: "10% after May 5" 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 October 6" 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 Forest Grove, ORNumbered nearest stations: 1 — near Vernonia, OR — 24 mi; 2 — Vancouver, WA — 24 mi; 3 — Portland, OR — 25 mi; 4 — Battle Ground, WA — 33 mi; 5 — Silverton, OR — 39 mi.ORWA25 mi · 40 km1. near Vernonia, OR — 24 mi12. Vancouver, WA — 24 mi23. Portland, OR — 25 mi34. Battle Ground, WA — 33 mi45. Silverton, OR — 39 mi5
  1. near Vernonia, OR 24 mi (38 km)
  2. Vancouver, WA 24 mi (39 km)
  3. Portland, OR 25 mi (40 km)
  4. Battle Ground, WA 33 mi (52 km)
  5. Silverton, OR 39 mi (63 km)

Sources

* Hardiness zone 8b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 45.5247, -123.1025.