U.S. Frost Dates by Weather Station

NOAA station USC00047109 · California

Frost Dates near Redwood Valley, CA

NOAA weather station Potter Valley Powerhouse (USC00047109), California · elevation 1018 ft (310 m) · hardiness zone 9a*

Redwood Valley is the nearest town to the station (7.8 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter April 29only 1 spring in 10 still has a frost later
  • Typical last frostApril 850% chance of a frost after it
  • Typical first fall frostNovember 650% chance of a frost before it
  • Frost-free season211 daystypical year, 32°F
  • Hardiness zone9acalculated*

The year at a glance

Frost season near Redwood Valley, CASpring: a frost after March 11 in 9 years out of 10, after April 8 in half of the years, after April 29 in 1 year out of 10. Fall: the first frost comes before October 20 in 1 year out of 10, before November 6 in half of the years, before November 24 in 9 years out of 10. Typical frost-free season: 211 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 8First frost ~Nov 6Frost season near Redwood Valley, CASpring: a frost after March 11 in 9 years out of 10, after April 8 in half of the years, after April 29 in 1 year out of 10. Fall: the first frost comes before October 20 in 1 year out of 10, before November 6 in half of the years, before November 24 in 9 years out of 10. Typical frost-free season: 211 days.JFMAMJJASONDLast frost ~Apr 8First frost ~Nov 6
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)April 29October 20
50% (typical)April 8November 6
90% (likely)March 11November 24
Frost-free season (32°F, 50% chance)
211 days
Hard frost (28°F), last in spring, 50% chance after
February 28
Hard frost (28°F), first in fall, 50% chance before
November 22

The last 15 years (2006–2020 normals)

Typical last frost April 5 (3 days earlier than the 30-year normal), typical first fall frost November 6. Frost-free season 214 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 near Redwood Valley: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 29, 20% April 22, 30% April 17, 40% April 12, 50% April 8, 60% April 4, 70% March 29, 80% March 22, 90% March 11. Observed last spring frost in recent years: 2021 March 23, 2022 May 10, 2023 April 5, 2024 April 6, 2025 March 18, 2026 January 24.Spring: last frostChance of a frost after this date10%50%90%Feb 1Mar 1Apr 1May 1Apr 29Apr 8Mar 112021: March 232022: May 102023: April 52024: April 62025: March 182026: January 24Fall near Redwood Valley: chance of a frost before this dateFall, chance of a frost before the date: 10% October 20, 20% October 27, 30% November 1, 40% November 3, 50% November 6, 60% November 9, 70% November 12, 80% November 17, 90% November 24. Observed first fall frost in recent years: 2021 October 12, 2022 November 3, 2023 October 27, 2024 October 29, 2025 November 25.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 20Nov 6Nov 242021: October 122022: November 32023: October 272024: October 292025: November 25
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
2021March 23October 12
2022May 10November 3
2023April 5October 27
2024April 6October 29
2025March 18November 25
2026January 24season not over yet

What these dates mean

The 211 days between the 32°F 50% dates in the Redwood Valley area frame the window when tender crops can be grown. The median dates are April 8 for spring and November 6 for fall; on each of those days there is an even chance of a light frost. The median hard-frost dates are February 28 in spring and November 22 in fall, marking the point where a 28°F frost is equally likely or unlikely.

For a cautious planting schedule, gardeners should wait until April 29, which carries only a 10 % chance that a light frost will occur later, before setting out tender crops. In the autumn they should aim to finish harvesting by October 20, when there is only a 10 % chance that a light frost has already arrived. A hard frost at 28 °F is more consequential than a light frost at 32 °F because the colder temperature can damage plant tissue that survives a milder freeze.

How to read the probabilities

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

  • Spring: "10% after April 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 October 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 Redwood Valley, CANumbered nearest stations: 1 — Graton, CA — 66 mi; 2 — Redding, CA — 91 mi; 3 — near Lewiston, CA — 96 mi; 4 — Strawberry Valley, CA — 109 mi; 5 — near Grass Valley, CA — 111 mi.CANV50 mi · 80 km1. Graton, CA — 66 mi12. Redding, CA — 91 mi23. near Lewiston, CA — 96 mi34. Strawberry Valley, CA — 109 mi45. near Grass Valley, CA — 111 mi5
  1. Graton, CA 66 mi (106 km)
  2. Redding, CA 91 mi (147 km)
  3. near Lewiston, CA 96 mi (154 km)
  4. Strawberry Valley, CA 109 mi (175 km)
  5. near Grass Valley, CA 111 mi (178 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: 39.3619, -123.1286.