U.S. Frost Dates by Weather Station

NOAA station USC00134585 · Iowa

Frost Dates for Lamoni, IA

NOAA weather station Lamoni (USC00134585), Iowa · elevation 1128 ft (344 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 1only 1 spring in 10 still has a frost later
  • Typical last frostApril 1750% chance of a frost after it
  • Typical first fall frostOctober 2150% chance of a frost before it
  • Frost-free season184 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Lamoni, IASpring: a frost after April 4 in 9 years out of 10, after April 17 in half of the years, after May 1 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 21 in half of the years, before November 2 in 9 years out of 10. Typical frost-free season: 184 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 17First frost ~Oct 21Frost season at Lamoni, IASpring: a frost after April 4 in 9 years out of 10, after April 17 in half of the years, after May 1 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 21 in half of the years, before November 2 in 9 years out of 10. Typical frost-free season: 184 days.JFMAMJJASONDLast frost ~Apr 17First frost ~Oct 21
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 1October 6
50% (typical)April 17October 21
90% (likely)April 4November 2
Frost-free season (32°F, 50% chance)
184 days
Hard frost (28°F), last in spring, 50% chance after
April 8
Hard frost (28°F), first in fall, 50% chance before
October 30

The last 15 years (2006–2020 normals)

Typical last frost April 18 (1 day later than the 30-year normal), typical first fall frost October 24 (3 days later). Frost-free season 187 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 Lamoni: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 1, 20% April 27, 30% April 23, 40% April 20, 50% April 17, 60% April 14, 70% April 12, 80% April 8, 90% April 4. Observed last spring frost in recent years: 2021 April 24, 2022 April 27, 2023 April 24, 2024 April 21, 2025 April 9, 2026 April 8.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 1Apr 17Apr 42021: April 242022: April 272023: April 242024: April 212025: April 92026: April 8Fall at Lamoni: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 11, 30% October 14, 40% October 18, 50% October 21, 60% October 24, 70% October 26, 80% October 29, 90% November 2. Observed first fall frost in recent years: 2021 November 2, 2022 October 9, 2023 October 28, 2024 October 16, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 21Nov 22021: November 22022: October 92023: October 282024: 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 24November 2
2022April 27October 9
2023April 24October 28
2024April 21October 16
2025April 9November 2
2026April 8season not over yet

What these dates mean

May 1 is the cautious spring light-frost date for Lamoni, Iowa; it carries only a 10 % chance that a frost will occur later, so a gardener can plan to set out tender crops with minimal risk. The 50 % light-frost date is April 17, meaning there is an even chance of a frost on either side of that day, while the median fall light-frost date is October 21, marking the point where the odds of a frost earlier or later are equal. October 6 is the cautious fall light-frost date, with a 10 % chance that a frost has already arrived, giving a gardener a reference for finishing the harvest of tender crops. The hard-frost 50 % dates are April 8 in spring and October 30 in fall; a hard frost at 28 °F can damage or kill plants that survive a light frost, making it a more critical threshold.

How to read the probabilities

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

  • Spring: "10% after May 1" 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 6" 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 Lamoni, IANumbered nearest stations: 1 — Beaconsfield, IA — 14 mi; 2 — Mount Ayr, IA — 17 mi; 3 — Bethany, MO — 26 mi; 4 — Spickard, MO — 28 mi; 5 — Osceola, IA — 29 mi.IA25 mi · 40 km1. Beaconsfield, IA — 14 mi12. Mount Ayr, IA — 17 mi23. Bethany, MO — 26 mi34. Spickard, MO — 28 mi45. Osceola, IA — 29 mi5
  1. Beaconsfield, IA 14 mi (23 km)
  2. Mount Ayr, IA 17 mi (28 km)
  3. Bethany, MO 26 mi (41 km)
  4. Spickard, MO 28 mi (46 km)
  5. Osceola, IA 29 mi (47 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: 40.6233, -93.9342.