U.S. Frost Dates by Weather Station

NOAA station USC00138568 · Iowa

Frost Dates for Vinton, IA

NOAA weather station Vinton (USC00138568), Iowa · elevation 850 ft (259 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 350% chance of a frost after it
  • Typical first fall frostOctober 350% chance of a frost before it
  • Frost-free season151 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Vinton, IASpring: a frost after April 21 in 9 years out of 10, after May 3 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 15 in 9 years out of 10. Typical frost-free season: 151 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 3First frost ~Oct 3Frost season at Vinton, IASpring: a frost after April 21 in 9 years out of 10, after May 3 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 15 in 9 years out of 10. Typical frost-free season: 151 days.JFMAMJJASONDLast frost ~May 3First 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.

Frost dates (32°F)

Probability of frost, based on 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 17September 20
50% (typical)May 3October 3
90% (likely)April 21October 15
Frost-free season (32°F, 50% chance)
151 days
Hard frost (28°F), last in spring, 50% chance after
April 25
Hard frost (28°F), first in fall, 50% chance before
October 12

The last 15 years (2006–2020 normals)

Typical last frost May 4 (1 day later than the 30-year normal), typical first fall frost October 8 (5 days later). Frost-free season 156 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 Vinton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 12, 30% May 9, 40% May 6, 50% May 3, 60% May 1, 70% April 29, 80% April 26, 90% April 21. Observed last spring frost in recent years: 2022 May 4, 2023 May 5, 2024 April 22, 2025 April 17, 2026 May 11.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 3Apr 212022: May 42023: May 52024: April 222025: April 172026: May 11Fall at Vinton: 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 6, 70% October 8, 80% October 11, 90% October 15. Observed first fall frost in recent years: 2021 October 22, 2022 September 27, 2023 October 9, 2024 October 7.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 20Oct 3Oct 152021: October 222022: September 272023: October 92024: October 7
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
2021incomplete recordOctober 22
2022May 4September 27
2023May 5October 9
2024April 22October 7
2025April 17incomplete record
2026May 11season not over yet

What these dates mean

Setting out tender crops on April 21 in Vinton is a gamble, because there is a 90% chance of a frost later than that date. The 50% date is May 3; at that point a gardener faces an even chance of a frost later in the season. The 50% date is October 3; at that point there is an even chance of a frost earlier in the season.

A cautious plan would wait until the May 17 light-frost date, which carries only a 10% chance of a frost later, and would aim to finish tender crops by the September 20 light-frost date, which carries only a 10% chance of a frost earlier. Hard frost at 28°F, marked by the dates April 25 and October 12, can injure plants that survive the milder 32°F light frost, so it is 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 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 Vinton, IANumbered nearest stations: 1 — near Marion, IA — 23 mi; 2 — Belle Plaine, IA — 24 mi; 3 — Cedar Rapids, IA — 25 mi; 4 — Toledo, IA — 31 mi; 5 — Waterloo, IA — 33 mi.WI25 mi · 40 km1. near Marion, IA — 23 mi12. Belle Plaine, IA — 24 mi23. Cedar Rapids, IA — 25 mi34. Toledo, IA — 31 mi45. Waterloo, IA — 33 mi5
  1. near Marion, IA 23 mi (37 km)
  2. Belle Plaine, IA 24 mi (39 km)
  3. Cedar Rapids, IA 25 mi (40 km)
  4. Toledo, IA 31 mi (50 km)
  5. Waterloo, IA 33 mi (54 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: 42.1703, -92.0078.