U.S. Frost Dates by Weather Station

NOAA station USC00136566 · Iowa

Frost Dates for Perry, IA

NOAA weather station Perry (USC00136566), Iowa · elevation 950 ft (290 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 8only 1 spring in 10 still has a frost later
  • Typical last frostApril 2550% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season166 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Perry, IASpring: a frost after April 12 in 9 years out of 10, after April 25 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 10 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 166 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 25First frost ~Oct 10Frost season at Perry, IASpring: a frost after April 12 in 9 years out of 10, after April 25 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 10 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 166 days.JFMAMJJASONDLast frost ~Apr 25First frost ~Oct 10
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 8September 25
50% (typical)April 25October 10
90% (likely)April 12October 24
Frost-free season (32°F, 50% chance)
166 days
Hard frost (28°F), last in spring, 50% chance after
April 16
Hard frost (28°F), first in fall, 50% chance before
October 22

The last 15 years (2006–2020 normals)

Typical last frost April 27 (2 days later than the 30-year normal), typical first fall frost October 14 (4 days later). Frost-free season 169 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 Perry: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 8, 20% May 5, 30% May 2, 40% April 28, 50% April 25, 60% April 22, 70% April 19, 80% April 16, 90% April 12. Observed last spring frost in recent years: 2021 April 23, 2023 May 4.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 8Apr 25Apr 122021: April 232023: May 4Fall at Perry: chance of a frost before this dateFall, chance of a frost before the date: 10% September 25, 20% September 30, 30% October 3, 40% October 7, 50% October 10, 60% October 13, 70% October 16, 80% October 19, 90% October 24. Observed first fall frost in recent years: 2021 October 22, 2022 October 8, 2023 October 10.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 25Oct 10Oct 242021: October 222022: October 82023: October 10
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 23October 22
2022incomplete recordOctober 8
2023May 4October 10
2024incomplete recordincomplete record
2025incomplete recordincomplete record
2026incomplete recordseason not over yet

What these dates mean

September 25 is the cautious fall date in Perry for finishing the harvest of tender crops, because only a 10 % chance exists that a light frost has occurred earlier. In spring, the cautious date for setting out tender crops is May 8, when the chance of a light frost later than that date is just 10 %, while planting on April 12 carries a 90 % chance and is a gamble.

The 50 % spring light-frost date is April 25, where the probability of a frost is 50 %; the 50 % fall light-frost date is October 10, also with a 50 % chance. The median hard-frost dates are April 16 in spring and October 22 in fall; a hard frost at 28 °F can damage plants more severely than a light frost at 32 °F. The record spans 30 years and the interval between the two 32 °F 50 % dates is 166 days.

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 25" 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 Perry, IANumbered nearest stations: 1 — Boone, IA — 18 mi; 2 — Jefferson, IA — 19 mi; 3 — Ames, IA — 21 mi; 4 — Guthrie Center, IA — 23 mi; 5 — Ankeny, IA — 25 mi.25 mi · 40 km1. Boone, IA — 18 mi12. Jefferson, IA — 19 mi23. Ames, IA — 21 mi34. Guthrie Center, IA — 23 mi45. Ankeny, IA — 25 mi5
  1. Boone, IA 18 mi (29 km)
  2. Jefferson, IA 19 mi (30 km)
  3. Ames, IA 21 mi (34 km)
  4. Guthrie Center, IA 23 mi (37 km)
  5. Ankeny, IA 25 mi (40 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: 41.8394, -94.1106.