U.S. Frost Dates by Weather Station

NOAA station USC00135796 · Iowa

Frost Dates for Mount Pleasant, IA

NOAA weather station Mount Pleasant 1 SSW (USC00135796), Iowa · elevation 730 ft (223 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season163 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Mount Pleasant, IASpring: a frost after April 13 in 9 years out of 10, after April 30 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 10 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 163 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 30First frost ~Oct 10Frost season at Mount Pleasant, IASpring: a frost after April 13 in 9 years out of 10, after April 30 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 24 in 1 year out of 10, before October 10 in half of the years, before October 23 in 9 years out of 10. Typical frost-free season: 163 days.JFMAMJJASONDLast frost ~Apr 30First 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 14September 24
50% (typical)April 30October 10
90% (likely)April 13October 23
Frost-free season (32°F, 50% chance)
163 days
Hard frost (28°F), last in spring, 50% chance after
April 17
Hard frost (28°F), first in fall, 50% chance before
October 20

The last 15 years (2006–2020 normals)

Typical last frost April 30 (same as the 30-year normal), typical first fall frost October 14 (4 days later). Frost-free season 167 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 Mount Pleasant: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 9, 30% May 6, 40% May 3, 50% April 30, 60% April 27, 70% April 22, 80% April 18, 90% April 13. Observed last spring frost in recent years: 2021 April 22, 2022 April 27, 2024 April 21, 2025 April 9.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 14Apr 30Apr 132021: April 222022: April 272024: April 212025: April 9Fall at Mount Pleasant: chance of a frost before this dateFall, chance of a frost before the date: 10% September 24, 20% September 29, 30% October 3, 40% October 7, 50% October 10, 60% October 12, 70% October 15, 80% October 18, 90% October 23. Observed first fall frost in recent years: 2021 November 1, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 24Oct 10Oct 232021: November 12024: October 162025: October 24
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 22November 1
2022April 27incomplete record
2023no dataincomplete record
2024April 21October 16
2025April 9October 24
2026incomplete recordseason not over yet

What these dates mean

The 163 days between the 50% dates in Mount Pleasant frame the window when light frosts are less likely. April 30 marks the point at which there is an even chance of a 32 °F frost later in spring, and October 10 marks the point at which there is an even chance of a 32 °F frost earlier in fall. These median dates are not frost dates themselves but help gauge risk.

For a cautious spring schedule, the 10 % chance date of May 14 is used to set out tender crops, while the 90 % chance date of April 13 would be a gamble. In the fall, the cautious date of September 24 signals when there is only a 10 % chance that a light frost has arrived, and waiting until October 23 would be risky. Hard frost at 28 °F, with its 50% dates of April 17 and October 20, can damage vegetation more severely than a light frost.

How to read the probabilities

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

  • Spring: "10% after May 14" 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 Mount Pleasant, IANumbered nearest stations: 1 — Fairfield, IA — 21 mi; 2 — Washington, IA — 24 mi; 3 — Fort Madison, IA — 26 mi; 4 — Burlington (Airport), IA — 26 mi; 5 — Keosauqua, IA — 26 mi.IAILMO25 mi · 40 km1. Fairfield, IA — 21 mi12. Washington, IA — 24 mi23. Fort Madison, IA — 26 mi34. Burlington (Airport), IA — 26 mi45. Keosauqua, IA — 26 mi5
  1. Fairfield, IA 21 mi (34 km)
  2. Washington, IA 24 mi (39 km)
  3. Fort Madison, IA 26 mi (41 km)
  4. Burlington (Airport), IA 26 mi (41 km)
  5. Keosauqua, IA 26 mi (41 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: 40.9486, -91.5647.