U.S. Frost Dates by Weather Station

NOAA station USC00134063 · Iowa

Frost Dates for Indianola, IA

NOAA weather station Indianola 2 W (USC00134063), Iowa · elevation 924 ft (282 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 8only 1 spring in 10 still has a frost later
  • Typical last frostApril 2450% 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 Indianola, IASpring: a frost after April 11 in 9 years out of 10, after April 24 in half of the years, after May 8 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 26 in 9 years out of 10. Typical frost-free season: 168 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 24First frost ~Oct 12Frost season at Indianola, IASpring: a frost after April 11 in 9 years out of 10, after April 24 in half of the years, after May 8 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 26 in 9 years out of 10. Typical frost-free season: 168 days.JFMAMJJASONDLast frost ~Apr 24First 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.

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 8September 27
50% (typical)April 24October 12
90% (likely)April 11October 26
Frost-free season (32°F, 50% chance)
168 days
Hard frost (28°F), last in spring, 50% chance after
April 14
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost April 26 (2 days later than the 30-year normal), typical first fall frost October 14 (2 days later). Frost-free season 171 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 Indianola: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 8, 20% May 4, 30% May 1, 40% April 28, 50% April 24, 60% April 21, 70% April 18, 80% April 15, 90% April 11. Observed last spring frost in recent years: 2021 May 12, 2022 April 27.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 8Apr 24Apr 112021: May 122022: April 27Fall at Indianola: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% October 1, 30% October 6, 40% October 9, 50% October 12, 60% October 14, 70% October 18, 80% October 21, 90% October 26. Observed first fall frost in recent years: 2021 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 12Oct 262021: October 22
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 12October 22
2022April 27incomplete record
2023incomplete recordno data
2024no datano data
2025no datano data
2026no dataseason not over yet

What these dates mean

Setting out tender crops on April 11 in Indianola carries a 90 % chance of a light frost later, making it a gamble for growers. The cautious spring date is May 8, when only a 10 % chance of a light frost remains.

The 50 % light-frost dates are April 24 and October 12; at each of these dates there is an even chance of a frost occurring later in spring or earlier in fall. The median hard-frost dates are April 14 and October 21, indicating a 50 % chance of temperatures reaching 28 °F around those points.

In the fall the cautious date for finishing tender crops is September 27, with only a 10 % chance that a light frost has already arrived, while October 26 is a gamble with a 90 % chance of frost already present. A hard frost matters more than a light frost because 28 °F can injure plants that would survive the milder 32 °F event.

How to read the probabilities

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

  • Spring: "10% after May 8" 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 Indianola, IANumbered nearest stations: 1 — Des Moines, IA — 12 mi; 2 — Osceola, IA — 25 mi; 3 — Ankeny, IA — 25 mi; 4 — Chariton, IA — 31 mi; 5 — Newton, IA — 40 mi.IAMO25 mi · 40 km1. Des Moines, IA — 12 mi12. Osceola, IA — 25 mi23. Ankeny, IA — 25 mi34. Chariton, IA — 31 mi45. Newton, IA — 40 mi5
  1. Des Moines, IA 12 mi (19 km)
  2. Osceola, IA 25 mi (40 km)
  3. Ankeny, IA 25 mi (41 km)
  4. Chariton, IA 31 mi (50 km)
  5. Newton, IA 40 mi (64 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: 41.3664, -93.6481.