U.S. Frost Dates by Weather Station

NOAA station USC00132999 · Iowa

Frost Dates for Fort Dodge, IA

NOAA weather station Fort Dodge 5 NNW (USC00132999), Iowa · elevation 1115 ft (340 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 9only 1 spring in 10 still has a frost later
  • Typical last frostApril 2850% chance of a frost after it
  • Typical first fall frostOctober 850% chance of a frost before it
  • Frost-free season162 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Fort Dodge, IASpring: a frost after April 13 in 9 years out of 10, after April 28 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 8 in half of the years, before October 22 in 9 years out of 10. Typical frost-free season: 162 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 28First frost ~Oct 8Frost season at Fort Dodge, IASpring: a frost after April 13 in 9 years out of 10, after April 28 in half of the years, after May 9 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 8 in half of the years, before October 22 in 9 years out of 10. Typical frost-free season: 162 days.JFMAMJJASONDLast frost ~Apr 28First frost ~Oct 8
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 9September 24
50% (typical)April 28October 8
90% (likely)April 13October 22
Frost-free season (32°F, 50% chance)
162 days
Hard frost (28°F), last in spring, 50% chance after
April 17
Hard frost (28°F), first in fall, 50% chance before
October 19

The last 15 years (2006–2020 normals)

Typical last frost April 29 (1 day later than the 30-year normal), typical first fall frost October 12 (4 days later). 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 Fort Dodge: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 9, 20% May 5, 30% May 3, 40% April 30, 50% April 28, 60% April 25, 70% April 22, 80% April 18, 90% April 13. Observed last spring frost in recent years: 2021 May 11, 2022 April 27, 2023 April 27, 2024 April 22, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 9Apr 28Apr 132021: May 112022: April 272023: April 272024: April 222026: May 7Fall at Fort Dodge: chance of a frost before this dateFall, chance of a frost before the date: 10% September 24, 20% September 29, 30% October 2, 40% October 5, 50% October 8, 60% October 11, 70% October 15, 80% October 18, 90% October 22. Observed first fall frost in recent years: 2021 October 22, 2022 September 28, 2023 October 10, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 24Oct 8Oct 222021: October 222022: September 282023: October 102025: October 23
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 11October 22
2022April 27September 28
2023April 27October 10
2024April 22incomplete record
2025incomplete recordOctober 23
2026May 7season not over yet

What these dates mean

September 24 is the cautious fall date to finish harvesting tender crops in Fort Dodge, because only a 10% chance of a light frost has occurred earlier.

The spring cautious date for setting out tender crops is May 9, when the chance of a light frost later is just 10%; planting on April 13 carries a 90% chance and is a gamble. The median light-frost dates are April 28 in spring and October 8 in fall, each representing an even 50% chance of a frost occurring on either side of the date.

Hard frost at 28°F is more damaging than a light frost at 32°F because it can freeze plant tissues that survive a milder chill; the 50% hard-frost dates are April 17 and October 19.

How to read the probabilities

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

  • Spring: "10% after May 9" 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 24" 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 Dodge, IANumbered nearest stations: 1 — Webster City, IA — 22 mi; 2 — Rockwell City, IA — 25 mi; 3 — Pocahontas, IA — 25 mi; 4 — Boone, IA — 41 mi; 5 — Jefferson, IA — 41 mi.IA25 mi · 40 km1. Webster City, IA — 22 mi12. Rockwell City, IA — 25 mi23. Pocahontas, IA — 25 mi34. Boone, IA — 41 mi45. Jefferson, IA — 41 mi5
  1. Webster City, IA 22 mi (35 km)
  2. Rockwell City, IA 25 mi (41 km)
  3. Pocahontas, IA 25 mi (41 km)
  4. Boone, IA 41 mi (65 km)
  5. Jefferson, IA 41 mi (66 km)

Sources

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

Station coordinates: 42.5836, -94.2006.