U.S. Frost Dates by Weather Station

NOAA station USC00132789 · Iowa

Frost Dates for Fairfield, IA

NOAA weather station Fairfield (USC00132789), Iowa · elevation 740 ft (226 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostApril 2750% chance of a frost after it
  • Typical first fall frostOctober 1250% chance of a frost before it
  • Frost-free season168 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Fairfield, IASpring: a frost after April 13 in 9 years out of 10, after April 27 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 12 in half of the years, before October 25 in 9 years out of 10. Typical frost-free season: 168 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 27First frost ~Oct 12Frost season at Fairfield, IASpring: a frost after April 13 in 9 years out of 10, after April 27 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 12 in half of the years, before October 25 in 9 years out of 10. Typical frost-free season: 168 days.JFMAMJJASONDLast frost ~Apr 27First frost ~Oct 12
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 14September 27
50% (typical)April 27October 12
90% (likely)April 13October 25
Frost-free season (32°F, 50% chance)
168 days
Hard frost (28°F), last in spring, 50% chance after
April 15
Hard frost (28°F), first in fall, 50% chance before
October 22

The last 15 years (2006–2020 normals)

Typical last frost April 25 (2 days earlier than the 30-year normal), typical first fall frost October 16 (4 days later). Frost-free season 173 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 Fairfield: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 8, 30% May 3, 40% April 30, 50% April 27, 60% April 24, 70% April 21, 80% April 17, 90% April 13. Observed last spring frost in recent years: 2021 April 25, 2022 April 26, 2023 April 24, 2024 April 21, 2025 April 10, 2026 April 21.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 14Apr 27Apr 132021: April 252022: April 262023: April 242024: April 212025: April 102026: April 21Fall at Fairfield: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% October 2, 30% October 6, 40% October 9, 50% October 12, 60% October 15, 70% October 18, 80% October 20, 90% October 25. Observed first fall frost in recent years: 2021 November 1, 2022 October 8, 2023 October 30, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 12Oct 252021: November 12022: October 82023: October 302024: October 162025: October 24
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 25November 1
2022April 26October 8
2023April 24October 30
2024April 21October 16
2025April 10October 24
2026April 21season not over yet

What these dates mean

September 27 marks the cautious fall date in Fairfield, the point at which there is only a 10 % chance that a light frost has arrived and tender crops should be harvested.

The 50% date is October 12; at that point a gardener faces a 50 % chance of a light frost occurring earlier. In spring the 50% date is April 27, indicating a 50 % chance of a light frost later than this date. For a low-risk plan the cautious spring date is May 14, when only a 10 % chance of a later light frost remains, while the early April 13 date carries a 90 % chance and is a gamble for tender crops.

A hard frost at 28 °F can damage plants that would otherwise survive a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after May 14" 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 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 Fairfield, IANumbered nearest stations: 1 — Keosauqua, IA — 20 mi; 2 — Mount Pleasant, IA — 21 mi; 3 — Washington, IA — 22 mi; 4 — Sigourney, IA — 26 mi; 5 — near Ottumwa, IA — 26 mi.IL25 mi · 40 km1. Keosauqua, IA — 20 mi12. Mount Pleasant, IA — 21 mi23. Washington, IA — 22 mi34. Sigourney, IA — 26 mi45. near Ottumwa, IA — 26 mi5
  1. Keosauqua, IA 20 mi (32 km)
  2. Mount Pleasant, IA 21 mi (34 km)
  3. Washington, IA 22 mi (36 km)
  4. Sigourney, IA 26 mi (42 km)
  5. near Ottumwa, IA 26 mi (42 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.0211, -91.9553.