U.S. Frost Dates by Weather Station

NOAA station USC00356366 · Oregon

Frost Dates for Otis, OR

NOAA weather station Otis 2 NE (USC00356366), Oregon · elevation 150 ft (46 m) · hardiness zone 9a*

  • Lower-risk planting dateafter May 3only 1 spring in 10 still has a frost later
  • Typical last frostApril 450% chance of a frost after it
  • Typical first fall frostNovember 1650% chance of a frost before it
  • Frost-free season227 daystypical year, 32°F
  • Hardiness zone9acalculated*

The year at a glance

Frost season at Otis, ORSpring: a frost after March 2 in 9 years out of 10, after April 4 in half of the years, after May 3 in 1 year out of 10. Fall: the first frost comes before October 26 in 1 year out of 10, before November 16 in half of the years, before December 12 in 9 years out of 10. Typical frost-free season: 227 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 4First frost ~Nov 16Frost season at Otis, ORSpring: a frost after March 2 in 9 years out of 10, after April 4 in half of the years, after May 3 in 1 year out of 10. Fall: the first frost comes before October 26 in 1 year out of 10, before November 16 in half of the years, before December 12 in 9 years out of 10. Typical frost-free season: 227 days.JFMAMJJASONDLast frost ~Apr 4First frost ~Nov 16
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 3October 26
50% (typical)April 4November 16
90% (likely)March 2December 12
Frost-free season (32°F, 50% chance)
227 days
Hard frost (28°F), last in spring, 50% chance after
February 18
Hard frost (28°F), first in fall, 50% chance before
December 8

The last 15 years (2006–2020 normals)

Typical last frost April 3 (1 day earlier than the 30-year normal), typical first fall frost November 18 (2 days later). Frost-free season 225 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 Otis: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 3, 20% April 27, 30% April 18, 40% April 11, 50% April 4, 60% March 31, 70% March 25, 80% March 19, 90% March 2. Observed last spring frost in recent years: 2021 April 11, 2022 April 17, 2023 April 12.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1May 1May 3Apr 4Mar 22021: April 112022: April 172023: April 12Fall at Otis: chance of a frost before this dateFall, chance of a frost before the date: 10% October 26, 20% November 1, 30% November 8, 40% November 12, 50% November 16, 60% November 22, 70% November 27, 80% December 2, 90% December 12. Observed first fall frost in recent years: 2021 November 22, 2022 November 9, 2023 October 28.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 26Nov 16Dec 122021: November 222022: November 92023: October 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
2021April 11November 22
2022April 17November 9
2023April 12October 28
2024incomplete recordno data
2025no datano data
2026no dataseason not over yet

What these dates mean

Setting out tender crops on the early spring date of March 2 in Otis carries a gamble, because a light frost still has a 90% chance of occurring later that season.

The 50% date is April 4, a 50% chance of a light frost later than this date in spring, and the 50% date is November 16, a 50% chance of a light frost earlier than this date in fall. The 50% hard-frost date in spring is February 18 and the 50% hard-frost date in fall is December 8. The cautious spring date for tender crops is May 3, when only a 10% chance of a light frost remains later, and the cautious fall date is October 26, when only a 10% chance of a light frost has arrived earlier.

A hard frost at 28 °F can injure plants that tolerate a light frost at 32 °F, making the hard-frost dates especially significant for protecting tender crops.

How to read the probabilities

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

  • Spring: "10% after May 3" 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 26" 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 Otis, ORNumbered nearest stations: 1 — Dallas, OR — 31 mi; 2 — near Corvallis, OR — 45 mi; 3 — Forest Grove, OR — 52 mi; 4 — Silverton, OR — 56 mi; 5 — Stayton, OR — 57 mi.WA25 mi · 40 km1. Dallas, OR — 31 mi12. near Corvallis, OR — 45 mi23. Forest Grove, OR — 52 mi34. Silverton, OR — 56 mi45. Stayton, OR — 57 mi5
  1. Dallas, OR 31 mi (51 km)
  2. near Corvallis, OR 45 mi (73 km)
  3. Forest Grove, OR 52 mi (84 km)
  4. Silverton, OR 56 mi (90 km)
  5. Stayton, OR 57 mi (91 km)

Sources

* Hardiness zone 9a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 45.0333, -123.9239.