U.S. Frost Dates by Weather Station

NOAA station USC00041277 · California

Frost Dates for Calaveras Big Trees, CA

NOAA weather station Calaveras Big Trees (USC00041277), California · elevation 4695 ft (1431 m) · hardiness zone 8a*

  • Lower-risk planting dateafter May 31only 1 spring in 10 still has a frost later
  • Typical last frostMay 750% chance of a frost after it
  • Typical first fall frostOctober 2850% chance of a frost before it
  • Frost-free season169 daystypical year, 32°F
  • Hardiness zone8acalculated*

The year at a glance

Frost season at Calaveras Big Trees, CASpring: a frost after April 18 in 9 years out of 10, after May 7 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 28 in half of the years, before November 16 in 9 years out of 10. Typical frost-free season: 169 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 7First frost ~Oct 28Frost season at Calaveras Big Trees, CASpring: a frost after April 18 in 9 years out of 10, after May 7 in half of the years, after May 31 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 28 in half of the years, before November 16 in 9 years out of 10. Typical frost-free season: 169 days.JFMAMJJASONDLast frost ~May 7First frost ~Oct 28
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 31October 5
50% (typical)May 7October 28
90% (likely)April 18November 16
Frost-free season (32°F, 50% chance)
169 days
Hard frost (28°F), last in spring, 50% chance after
April 18
Hard frost (28°F), first in fall, 50% chance before
November 14

The last 15 years (2006–2020 normals)

Typical last frost May 11 (4 days later than the 30-year normal), typical first fall frost October 26 (2 days earlier). Frost-free season 166 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 Calaveras Big Trees: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 31, 20% May 25, 30% May 18, 40% May 13, 50% May 7, 60% May 2, 70% April 29, 80% April 24, 90% April 18.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 31May 7Apr 18Fall at Calaveras Big Trees: chance of a frost before this dateFall, chance of a frost before the date: 10% October 5, 20% October 12, 30% October 18, 40% October 23, 50% October 28, 60% November 1, 70% November 5, 80% November 9, 90% November 16.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 5Oct 28Nov 16
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.

What these dates mean

The cautious fall date to finish harvesting tender crops at Calaveras Big Trees is October 5, when there is only a 10 % chance a light frost has arrived.

For a gardener, the 50 % dates represent the point at which a light frost is equally likely to have occurred or not. The median light-frost dates are May 7 in spring and October 28 in fall; they are not frost dates themselves. The corresponding hard-frost 50 % dates are April 18 and November 14, marking the middle of the range for temperatures dropping to 28 °F.

In spring the cautious date for setting out tender crops is May 31, which carries a 10 % chance of a later frost, while the fall cautious date is October 5. A hard frost matters more than a light frost because 28 °F can damage or kill plants that survive the milder 32 °F conditions.

How to read the probabilities

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

  • Spring: "10% after May 31" 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 5" 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 Calaveras Big Trees, CANumbered nearest stations: 1 — Sonora, CA — 22 mi; 2 — Cherry Valley Dam, CA — 30 mi; 3 — Minden, NV — 55 mi; 4 — Tahoe City, CA — 62 mi; 5 — Smith, NV — 67 mi.CANV25 mi · 40 km1. Sonora, CA — 22 mi12. Cherry Valley Dam, CA — 30 mi23. Minden, NV — 55 mi34. Tahoe City, CA — 62 mi45. Smith, NV — 67 mi5
  1. Sonora, CA 22 mi (35 km)
  2. Cherry Valley Dam, CA 30 mi (48 km)
  3. Minden, NV 55 mi (89 km)
  4. Tahoe City, CA 62 mi (100 km)
  5. Smith, NV 67 mi (107 km)

Sources

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

Station coordinates: 38.2769, -120.3114.