U.S. Frost Dates by Weather Station

NOAA station USC00454154 · Washington

Frost Dates for Kennewick, WA

NOAA weather station Kennewick (USC00454154), Washington · elevation 390 ft (119 m) · hardiness zone 7b*

  • Lower-risk planting dateafter April 10only 1 spring in 10 still has a frost later
  • Typical last frostMarch 2850% chance of a frost after it
  • Typical first fall frostOctober 3050% chance of a frost before it
  • Frost-free season216 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Kennewick, WASpring: a frost after March 9 in 9 years out of 10, after March 28 in half of the years, after April 10 in 1 year out of 10. Fall: the first frost comes before October 18 in 1 year out of 10, before October 30 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 216 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Mar 28First frost ~Oct 30Frost season at Kennewick, WASpring: a frost after March 9 in 9 years out of 10, after March 28 in half of the years, after April 10 in 1 year out of 10. Fall: the first frost comes before October 18 in 1 year out of 10, before October 30 in half of the years, before November 15 in 9 years out of 10. Typical frost-free season: 216 days.JFMAMJJASONDLast frost ~Mar 28First frost ~Oct 30
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 10October 18
50% (typical)March 28October 30
90% (likely)March 9November 15
Frost-free season (32°F, 50% chance)
216 days
Hard frost (28°F), last in spring, 50% chance after
March 8
Hard frost (28°F), first in fall, 50% chance before
November 11

The last 15 years (2006–2020 normals)

Typical last frost March 29 (1 day later than the 30-year normal), typical first fall frost October 31 (1 day later). Frost-free season 216 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 Kennewick: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 10, 20% April 5, 30% April 2, 40% March 31, 50% March 28, 60% March 25, 70% March 21, 80% March 15, 90% March 9. Observed last spring frost in recent years: 2021 April 13, 2022 March 11, 2023 March 18, 2024 March 16, 2025 March 7, 2026 March 28.Spring: last frostChance of a frost after this date10%50%90%Mar 1Apr 1Apr 10Mar 28Mar 92021: April 132022: March 112023: March 182024: March 162025: March 72026: March 28Fall at Kennewick: chance of a frost before this dateFall, chance of a frost before the date: 10% October 18, 20% October 22, 30% October 25, 40% October 28, 50% October 30, 60% November 2, 70% November 5, 80% November 10, 90% November 15. Observed first fall frost in recent years: 2021 November 17, 2022 November 4, 2023 October 28, 2024 November 6, 2025 November 30.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 18Oct 30Nov 152021: November 172022: November 42023: October 282024: November 62025: 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 13November 17
2022March 11November 4
2023March 18October 28
2024March 16November 6
2025March 7November 30
2026March 28season not over yet

What these dates mean

Setting out tender crops on March 9 in Kennewick is a gamble, as it carries a 90 % chance of a light frost later that season.

The cautious spring date is April 10, when only a 10 % chance of a light frost remains, and the cautious fall date is October 18, when there is only a 10 % chance that a light frost has already arrived. The 50 % date is March 28; at that point a gardener faces an even chance of a light frost later. The 50 % date is October 30; at that point there is an even chance of a light frost earlier. Hard-frost median dates are March 8 and November 11.

A hard frost at 28 °F, which can occur around those median dates, is more damaging than a light frost at 32 °F because the lower temperature can kill plant tissue that survives the milder chill.

How to read the probabilities

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

  • Spring: "10% after April 10" 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 18" 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 Kennewick, WANumbered nearest stations: 1 — Richland, WA — 10 mi; 2 — near Burbank, WA — 11 mi; 3 — Whitman Mission, WA — 33 mi; 4 — Pendleton, OR — 38 mi; 5 — Boardman, OR — 38 mi.25 mi · 40 km1. Richland, WA — 10 mi12. near Burbank, WA — 11 mi23. Whitman Mission, WA — 33 mi34. Pendleton, OR — 38 mi45. Boardman, OR — 38 mi5
  1. Richland, WA 10 mi (17 km)
  2. near Burbank, WA 11 mi (18 km)
  3. Whitman Mission, WA 33 mi (53 km)
  4. Pendleton, OR 38 mi (61 km)
  5. Boardman, OR 38 mi (61 km)

Sources

* Hardiness zone 7b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 46.2111, -119.1011.