U.S. Frost Dates by Weather Station

NOAA station USC00133584 · Iowa

Frost Dates for Hampton, IA

NOAA weather station Hampton (USC00133584), Iowa · elevation 1105 ft (337 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 10only 1 spring in 10 still has a frost later
  • Typical last frostApril 2950% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season162 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Hampton, IASpring: a frost after April 15 in 9 years out of 10, after April 29 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 9 in half of the years, before October 22 in 9 years out of 10. Typical frost-free season: 162 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 29First frost ~Oct 9Frost season at Hampton, IASpring: a frost after April 15 in 9 years out of 10, after April 29 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 9 in half of the years, before October 22 in 9 years out of 10. Typical frost-free season: 162 days.JFMAMJJASONDLast frost ~Apr 29First frost ~Oct 9
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 10September 26
50% (typical)April 29October 9
90% (likely)April 15October 22
Frost-free season (32°F, 50% chance)
162 days
Hard frost (28°F), last in spring, 50% chance after
April 19
Hard frost (28°F), first in fall, 50% chance before
October 20

The last 15 years (2006–2020 normals)

Typical last frost April 30 (1 day later than the 30-year normal), typical first fall frost October 12 (3 days later). Frost-free season 165 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 Hampton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 10, 20% May 6, 30% May 3, 40% May 1, 50% April 29, 60% April 26, 70% April 23, 80% April 19, 90% April 15. Observed last spring frost in recent years: 2021 May 29, 2022 May 4, 2023 May 3, 2024 April 21, 2025 April 17, 2026 May 2.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Jun 1May 10Apr 29Apr 152021: May 292022: May 42023: May 32024: April 212025: April 172026: May 2Fall at Hampton: chance of a frost before this dateFall, chance of a frost before the date: 10% September 26, 20% September 30, 30% October 3, 40% October 5, 50% October 9, 60% October 11, 70% October 14, 80% October 17, 90% October 22. Observed first fall frost in recent years: 2021 October 23, 2022 September 28, 2023 October 11, 2024 October 15.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 9Oct 222021: October 232022: September 282023: October 112024: October 15
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 29October 23
2022May 4September 28
2023May 3October 11
2024April 21October 15
2025April 17incomplete record
2026May 2season not over yet

What these dates mean

Setting out tender crops on the early spring date, April 15, carries a 90% chance of a frost later in the season, making it a gamble for gardeners in Hampton.

The 50% date for light frost in spring is April 29; at that point there is a 50% chance of a frost later than this date, so it serves as a reference point rather than a target. A cautious planting plan uses the May 10 date, which has only a 10% chance of a later frost, while in fall the cautious date to finish harvesting tender crops is September 26, also with a 10% chance of an earlier frost.

Hard frost (28°F) matters more than light frost (32°F) because the lower temperature can cause more severe plant injury.

How to read the probabilities

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

  • Spring: "10% after May 10" 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 26" 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 Hampton, IANumbered nearest stations: 1 — Iowa Falls, IA — 17 mi; 2 — Allison, IA — 20 mi; 3 — Eldora, IA — 28 mi; 4 — Mason City, IA — 28 mi; 5 — Mason City (Airport), IA — 28 mi.MN25 mi · 40 km1. Iowa Falls, IA — 17 mi12. Allison, IA — 20 mi23. Eldora, IA — 28 mi34. Mason City, IA — 28 mi45. Mason City (Airport), IA — 28 mi5
  1. Iowa Falls, IA 17 mi (27 km)
  2. Allison, IA 20 mi (33 km)
  3. Eldora, IA 28 mi (44 km)
  4. Mason City, IA 28 mi (45 km)
  5. Mason City (Airport), IA 28 mi (45 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: 42.7561, -93.2019.