U.S. Frost Dates by Weather Station

NOAA station USC00046657 · California

Frost Dates near Aguanga, CA

NOAA weather station Palomar Mountain Obsy (USC00046657), California · elevation 5550 ft (1692 m) · hardiness zone 9a*

Aguanga is the nearest town to the station (4.7 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 May 29only 1 spring in 10 still has a frost later
  • Typical last frostApril 2950% chance of a frost after it
  • Typical first fall frostNovember 1850% chance of a frost before it
  • Frost-free season201 daystypical year, 32°F
  • Hardiness zone9acalculated*

The year at a glance

Frost season near Aguanga, CASpring: a frost after April 2 in 9 years out of 10, after April 29 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before October 27 in 1 year out of 10, before November 18 in half of the years, before December 8 in 9 years out of 10. Typical frost-free season: 201 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 29First frost ~Nov 18Frost season near Aguanga, CASpring: a frost after April 2 in 9 years out of 10, after April 29 in half of the years, after May 29 in 1 year out of 10. Fall: the first frost comes before October 27 in 1 year out of 10, before November 18 in half of the years, before December 8 in 9 years out of 10. Typical frost-free season: 201 days.JFMAMJJASONDLast frost ~Apr 29First frost ~Nov 18
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 29October 27
50% (typical)April 29November 18
90% (likely)April 2December 8
Frost-free season (32°F, 50% chance)
201 days
Hard frost (28°F), last in spring, 50% chance after
April 5
Hard frost (28°F), first in fall, 50% chance before
December 6

The last 15 years (2006–2020 normals)

Typical last frost April 30 (1 day later than the 30-year normal), typical first fall frost November 18. Frost-free season 202 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 Aguanga: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 29, 20% May 18, 30% May 10, 40% May 3, 50% April 29, 60% April 24, 70% April 17, 80% April 11, 90% April 2. Observed last spring frost in recent years: 2021 May 22, 2022 May 11, 2023 May 4, 2024 April 15, 2025 April 27, 2026 April 27.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Jun 1May 29Apr 29Apr 22021: May 222022: May 112023: May 42024: April 152025: April 272026: April 27Fall near Aguanga: chance of a frost before this dateFall, chance of a frost before the date: 10% October 27, 20% November 2, 30% November 8, 40% November 13, 50% November 18, 60% November 22, 70% November 27, 80% December 2, 90% December 8. Observed first fall frost in recent years: 2021 October 12, 2022 November 3, 2023 November 25, 2024 November 15, 2025 November 18.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 27Nov 18Dec 82021: October 122022: November 32023: November 252024: November 152025: November 18
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 22October 12
2022May 11November 3
2023May 4November 25
2024April 15November 15
2025April 27November 18
2026April 27season not over yet

What these dates mean

The 201 days between the 32°F 50% dates—April 29 in spring and November 18 in fall—frame the interval when a light frost is equally likely to have occurred or not. For a gardener these median dates are simply reference points; they are not themselves frost dates.

In the Aguanga area a cautious spring plan would wait until May 29, when there is only a 10 % chance of a frost later than that date, while a cautious fall plan would finish tender crops by October 27, when only a 10 % chance exists of a frost earlier than that date. Planting on April 2 carries a 90 % chance of a frost later, and staying out until December 8 carries a 90 % chance of a frost earlier, so both are gambles. Hard-frost dates—April 5 and December 6 for a 28 °F threshold—matter more because a hard frost can damage plants that survive a light frost.

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 October 27" 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 Aguanga, CANumbered nearest stations: 1 — Campo, CA — 56 mi; 2 — Big Bear Lake, CA — 60 mi; 3 — near Barstow, CA — 102 mi; 4 — Sandberg, CA — 143 mi; 5 — Pahrump, NV — 204 mi.CAAZNV100 mi · 161 km1. Campo, CA — 56 mi12. Big Bear Lake, CA — 60 mi23. near Barstow, CA — 102 mi34. Sandberg, CA — 143 mi45. Pahrump, NV — 204 mi5
  1. Campo, CA 56 mi (90 km)
  2. Big Bear Lake, CA 60 mi (96 km)
  3. near Barstow, CA 102 mi (164 km)
  4. Sandberg, CA 143 mi (231 km)
  5. Pahrump, NV 204 mi (328 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: 33.3781, -116.84.