U.S. Frost Dates by Weather Station

NOAA station USC00133509 · Iowa

Frost Dates for Guthrie Center, IA

NOAA weather station Guthrie Center (USC00133509), Iowa · elevation 1065 ft (325 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season153 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Guthrie Center, IASpring: a frost after April 18 in 9 years out of 10, after May 2 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 3 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 153 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 3Frost season at Guthrie Center, IASpring: a frost after April 18 in 9 years out of 10, after May 2 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before September 20 in 1 year out of 10, before October 3 in half of the years, before October 18 in 9 years out of 10. Typical frost-free season: 153 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 3
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 17September 20
50% (typical)May 2October 3
90% (likely)April 18October 18
Frost-free season (32°F, 50% chance)
153 days
Hard frost (28°F), last in spring, 50% chance after
April 23
Hard frost (28°F), first in fall, 50% chance before
October 15

The last 15 years (2006–2020 normals)

Typical last frost May 3 (1 day later than the 30-year normal), typical first fall frost October 9 (6 days later). Frost-free season 158 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 Guthrie Center: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 11, 30% May 8, 40% May 5, 50% May 2, 60% April 30, 70% April 26, 80% April 22, 90% April 18. Observed last spring frost in recent years: 2021 May 13, 2022 May 22, 2023 May 3, 2024 April 22, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 2Apr 182021: May 132022: May 222023: May 32024: April 222026: May 11Fall at Guthrie Center: chance of a frost before this dateFall, chance of a frost before the date: 10% September 20, 20% September 25, 30% September 28, 40% October 1, 50% October 3, 60% October 5, 70% October 10, 80% October 13, 90% October 18. Observed first fall frost in recent years: 2021 September 25, 2022 September 28, 2023 October 9, 2024 October 7, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 20Oct 3Oct 182021: September 252022: September 282023: October 92024: October 72025: 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 13September 25
2022May 22September 28
2023May 3October 9
2024April 22October 7
2025incomplete recordOctober 22
2026May 11season not over yet

What these dates mean

Setting out tender crops on the early spring date, April 18, is a gamble in Guthrie Center because there is a 90 % chance of a light frost later that day. The cautious alternative is the later May 17 date, which carries only a 10 % chance of a frost after it. In the fall, the risky choice is October 18, where a 90 % chance of a frost has already arrived, while the cautious date to finish harvesting tender crops is September 20, with only a 10 % chance of an earlier frost.

The 50 % dates for light frost are May 2 in spring and October 3 in fall; a gardener can expect an even odds of a frost occurring after May 2 or before October 3. The 50 % hard-frost dates are April 23 and October 15, and hard frost at 28 °F poses a greater risk to plant tissue than 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 17" 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 20" 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 Guthrie Center, IANumbered nearest stations: 1 — Audubon, IA — 22 mi; 2 — Perry, IA — 23 mi; 3 — Jefferson, IA — 24 mi; 4 — Greenfield, IA — 26 mi; 5 — Atlantic, IA — 31 mi.NE25 mi · 40 km1. Audubon, IA — 22 mi12. Perry, IA — 23 mi23. Jefferson, IA — 24 mi34. Greenfield, IA — 26 mi45. Atlantic, IA — 31 mi5
  1. Audubon, IA 22 mi (36 km)
  2. Perry, IA 23 mi (37 km)
  3. Jefferson, IA 24 mi (39 km)
  4. Greenfield, IA 26 mi (42 km)
  5. Atlantic, IA 31 mi (51 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: 41.6686, -94.4972.