U.S. Frost Dates by Weather Station

NOAA station USC00133007 · Iowa

Frost Dates for Fort Madison, IA

NOAA weather station Fort Madison (USC00133007), Iowa · elevation 530 ft (162 m) · hardiness zone 6a*

  • Lower-risk planting dateafter April 26only 1 spring in 10 still has a frost later
  • Typical last frostApril 1250% chance of a frost after it
  • Typical first fall frostOctober 2550% chance of a frost before it
  • Frost-free season194 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Fort Madison, IASpring: a frost after April 1 in 9 years out of 10, after April 12 in half of the years, after April 26 in 1 year out of 10. Fall: the first frost comes before October 11 in 1 year out of 10, before October 25 in half of the years, before November 6 in 9 years out of 10. Typical frost-free season: 194 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 12First frost ~Oct 25Frost season at Fort Madison, IASpring: a frost after April 1 in 9 years out of 10, after April 12 in half of the years, after April 26 in 1 year out of 10. Fall: the first frost comes before October 11 in 1 year out of 10, before October 25 in half of the years, before November 6 in 9 years out of 10. Typical frost-free season: 194 days.JFMAMJJASONDLast frost ~Apr 12First frost ~Oct 25
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 26October 11
50% (typical)April 12October 25
90% (likely)April 1November 6
Frost-free season (32°F, 50% chance)
194 days
Hard frost (28°F), last in spring, 50% chance after
April 3
Hard frost (28°F), first in fall, 50% chance before
November 4

The last 15 years (2006–2020 normals)

Typical last frost April 13 (1 day later than the 30-year normal), typical first fall frost October 26 (1 day later). Frost-free season 194 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 Fort Madison: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 26, 20% April 22, 30% April 18, 40% April 15, 50% April 12, 60% April 10, 70% April 7, 80% April 4, 90% April 1. Observed last spring frost in recent years: 2021 April 22, 2022 April 26, 2023 April 6, 2024 March 27, 2026 March 28.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 26Apr 12Apr 12021: April 222022: April 262023: April 62024: March 272026: March 28Fall at Fort Madison: chance of a frost before this dateFall, chance of a frost before the date: 10% October 11, 20% October 17, 30% October 20, 40% October 23, 50% October 25, 60% October 27, 70% October 30, 80% November 2, 90% November 6. Observed first fall frost in recent years: 2021 November 2, 2022 October 17, 2023 October 29, 2024 October 16, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 11Oct 25Nov 62021: November 22022: October 172023: October 292024: October 162025: November 2
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 22November 2
2022April 26October 17
2023April 6October 29
2024March 27October 16
2025incomplete recordNovember 2
2026March 28season not over yet

What these dates mean

Planting tender crops on the early spring date of April 1 in Fort Madison carries a 90% chance of a light frost later, making it a gamble.

The 50% light-frost date of April 12 marks the point at which a frost is equally likely to occur later in spring, while the fall 50% date of October 25 marks the point at which a frost is equally likely to have arrived earlier. Likewise, the median hard-frost dates are April 3 in spring and November 4 in fall; these are the dates when a 28 °F frost is as probable as not.

A cautious spring schedule would wait until the April 26 date, which has only a 10% chance of a frost later, and a cautious fall finish would aim for October 11, which has only a 10% chance of a frost earlier. Hard frosts at 28 °F can damage plant tissue that survives a light 32 °F frost, so they represent a greater risk.

How to read the probabilities

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

  • Spring: "10% after April 26" 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 11" 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 Fort Madison, IANumbered nearest stations: 1 — near Burlington, IA — 16 mi; 2 — Burlington (Airport), IA — 16 mi; 3 — near Keokuk, IA — 16 mi; 4 — Bentley, IL — 22 mi; 5 — near Oquawka, IL — 24 mi.ILIAMO25 mi · 40 km1. near Burlington, IA — 16 mi12. Burlington (Airport), IA — 16 mi23. near Keokuk, IA — 16 mi34. Bentley, IL — 22 mi45. near Oquawka, IL — 24 mi5
  1. near Burlington, IA 16 mi (25 km)
  2. Burlington (Airport), IA 16 mi (25 km)
  3. near Keokuk, IA 16 mi (25 km)
  4. Bentley, IL 22 mi (36 km)
  5. near Oquawka, IL 24 mi (39 km)

Sources

* Hardiness zone 6a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 40.6222, -91.3339.