U.S. Frost Dates by Weather Station

NOAA station USC00135493 · Iowa

Frost Dates for Milford, IA

NOAA weather station Milford 4 NW (USC00135493), Iowa · elevation 1402 ft (427 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 150% chance of a frost after it
  • Typical first fall frostOctober 650% chance of a frost before it
  • Frost-free season158 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Milford, IASpring: a frost after April 17 in 9 years out of 10, after May 1 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 6 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 158 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 6Frost season at Milford, IASpring: a frost after April 17 in 9 years out of 10, after May 1 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 6 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 158 days.JFMAMJJASONDLast frost ~May 1First frost ~Oct 6
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 14September 24
50% (typical)May 1October 6
90% (likely)April 17October 21
Frost-free season (32°F, 50% chance)
158 days
Hard frost (28°F), last in spring, 50% chance after
April 21
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost April 29 (2 days earlier than the 30-year normal), typical first fall frost October 11 (5 days later). Frost-free season 164 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 Milford: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 9, 30% May 5, 40% May 3, 50% May 1, 60% April 28, 70% April 25, 80% April 22, 90% April 17. Observed last spring frost in recent years: 2021 May 5, 2022 May 22, 2023 April 26, 2024 April 21, 2025 April 21, 2026 May 6.Spring: last frostChance of a frost after this date10%50%90%May 1May 14May 1Apr 172021: May 52022: May 222023: April 262024: April 212025: April 212026: May 6Fall at Milford: chance of a frost before this dateFall, chance of a frost before the date: 10% September 24, 20% September 29, 30% October 1, 40% October 4, 50% October 6, 60% October 9, 70% October 13, 80% October 17, 90% October 21. Observed first fall frost in recent years: 2021 September 25, 2022 September 28, 2023 October 7, 2024 October 14, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 24Oct 6Oct 212021: September 252022: September 282023: October 72024: October 142025: 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 5September 25
2022May 22September 28
2023April 26October 7
2024April 21October 14
2025April 21October 22
2026May 6season not over yet

What these dates mean

Setting out tender crops on the early spring date of April 17 is a gamble, because a frost later that day occurs with a 90% chance. The cautious date for planting tender crops in Milford is May 14, when only a 10% chance of a later frost remains.

The 50% dates—May 1 in spring and October 6 in fall—mark the point where a frost is equally likely to occur later or earlier. For the autumn harvest, the cautious date to finish tender crops is September 24, with only a 10% chance that frost has arrived earlier.

Hard frosts, recorded at 28°F, are more damaging than light frosts at 32°F; the median hard-frost dates are April 21 and October 17. Generally.

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 Milford, IANumbered nearest stations: 1 — Lake Park, IA — 8 mi; 2 — Spencer, IA — 15 mi; 3 — Estherville, IA — 22 mi; 4 — Worthington, MN — 27 mi; 5 — Sanborn, IA — 28 mi.MN25 mi · 40 km1. Lake Park, IA — 8 mi12. Spencer, IA — 15 mi23. Estherville, IA — 22 mi34. Worthington, MN — 27 mi45. Sanborn, IA — 28 mi5
  1. Lake Park, IA 8 mi (13 km)
  2. Spencer, IA 15 mi (24 km)
  3. Estherville, IA 22 mi (35 km)
  4. Worthington, MN 27 mi (43 km)
  5. Sanborn, 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: 43.3828, -95.1842.