U.S. Frost Dates by Weather Station

NOAA station USW00023157 · California

Frost Dates for Bishop, CA

NOAA weather station Bishop Airport (USW00023157), California · elevation 4102 ft (1250 m) · hardiness zone 7b*

  • Lower-risk planting dateafter May 27only 1 spring in 10 still has a frost later
  • Typical last frostApril 2950% chance of a frost after it
  • Typical first fall frostOctober 1550% chance of a frost before it
  • Frost-free season166 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Bishop, CASpring: a frost after April 12 in 9 years out of 10, after April 29 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 15 in half of the years, before October 27 in 9 years out of 10. Typical frost-free season: 166 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 29First frost ~Oct 15Frost season at Bishop, CASpring: a frost after April 12 in 9 years out of 10, after April 29 in half of the years, after May 27 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 15 in half of the years, before October 27 in 9 years out of 10. Typical frost-free season: 166 days.JFMAMJJASONDLast frost ~Apr 29First frost ~Oct 15
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)May 27September 30
50% (typical)April 29October 15
90% (likely)April 12October 27
Frost-free season (32°F, 50% chance)
166 days
Hard frost (28°F), last in spring, 50% chance after
April 15
Hard frost (28°F), first in fall, 50% chance before
October 25

The last 15 years (2006–2020 normals)

Typical last frost April 30 (1 day later than the 30-year normal), typical first fall frost October 11 (4 days earlier). Frost-free season 164 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 Bishop: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 27, 20% May 15, 30% May 7, 40% May 2, 50% April 29, 60% April 26, 70% April 22, 80% April 18, 90% April 12. Observed last spring frost in recent years: 2021 May 23, 2022 June 18, 2023 May 8, 2024 May 7, 2025 April 27, 2026 May 19.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Jun 1May 27Apr 29Apr 122021: May 232022: June 182023: May 82024: May 72025: April 272026: May 19Fall at Bishop: chance of a frost before this dateFall, chance of a frost before the date: 10% September 30, 20% October 5, 30% October 9, 40% October 12, 50% October 15, 60% October 17, 70% October 20, 80% October 23, 90% October 27. Observed first fall frost in recent years: 2021 October 9, 2022 October 24, 2024 October 21, 2025 October 13.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 30Oct 15Oct 272021: October 92022: October 242024: October 212025: October 13
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 23October 9
2022June 18October 24
2023May 8incomplete record
2024May 7October 21
2025April 27October 13
2026May 19season not over yet

What these dates mean

The cautious fall date for finishing the harvest in Bishop is September 30, when there is only a 10% chance that a light frost has arrived.

In spring the 50% date is April 29, the point where the chance of a light frost is even, and the cautious date for setting out tender crops is May 27, which carries a 10% chance of a later frost. In fall the 50% date is October 15, the point where the chance of a light frost is even, and the cautious date for finishing tender-crop harvest is September 30, which carries a 10% chance of an earlier frost.

A hard frost at 28°F can injure plant tissue that survives a light frost at 32°F, so the median hard-frost dates of April 15 and October 25 signal a higher risk.

How to read the probabilities

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

  • Spring: "10% after May 27" 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 September 30" 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 Bishop, CANumbered nearest stations: 1 — Dyer, NV — 25 mi; 2 — Lodgepole, CA — 57 mi; 3 — Lee Vining, CA — 58 mi; 4 — Auberry, CA — 66 mi; 5 — Tonopah, NV — 84 mi.CANV25 mi · 40 km1. Dyer, NV — 25 mi12. Lodgepole, CA — 57 mi23. Lee Vining, CA — 58 mi34. Auberry, CA — 66 mi45. Tonopah, NV — 84 mi5
  1. Dyer, NV 25 mi (41 km)
  2. Lodgepole, CA 57 mi (92 km)
  3. Lee Vining, CA 58 mi (93 km)
  4. Auberry, CA 66 mi (107 km)
  5. Tonopah, NV 84 mi (135 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: 37.3711, -118.3581.