U.S. Frost Dates by Weather Station

NOAA station USC00138296 · Iowa

Frost Dates for Toledo, IA

NOAA weather station Toledo 3 N (USC00138296), Iowa · elevation 935 ft (285 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% 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 Toledo, IASpring: a frost after April 15 in 9 years out of 10, after April 30 in half of the years, after May 11 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 30First frost ~Oct 9Frost season at Toledo, IASpring: a frost after April 15 in 9 years out of 10, after April 30 in half of the years, after May 11 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 30First 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.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 11September 26
50% (typical)April 30October 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 29 (1 day earlier than the 30-year normal), typical first fall frost October 14 (5 days later). Frost-free season 168 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 Toledo: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 11, 20% May 7, 30% May 4, 40% May 2, 50% April 30, 60% April 27, 70% April 23, 80% April 20, 90% April 15. Observed last spring frost in recent years: 2021 April 26, 2022 April 27, 2023 May 4, 2024 April 22, 2025 April 17, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 11Apr 30Apr 152021: April 262022: April 272023: May 42024: April 222025: April 172026: May 3Fall at Toledo: 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 6, 50% October 9, 60% October 12, 70% October 14, 80% October 18, 90% October 22. Observed first fall frost in recent years: 2021 October 22, 2022 September 28, 2023 October 10, 2024 October 15, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 9Oct 222021: October 222022: September 282023: October 102024: October 152025: October 23
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 26October 22
2022April 27September 28
2023May 4October 10
2024April 22October 15
2025April 17October 23
2026May 3season not over yet

What these dates mean

May 11 is the cautious spring date, giving a 10% chance of a light frost later and allowing a gardener to set out tender crops with confidence. By contrast, April 15 carries a 90% chance and is a gamble for early planting. The 50% date is April 30, meaning there is an even chance of a light frost on either side of that day. The median hard-frost date in spring is April 19, which signals when a 28°F event becomes as likely as not.

September 26 is the cautious fall date, with a 10% chance of a light frost earlier and permitting the final harvest of tender crops. October 22 carries a 90% chance and is a gamble for extending the season. The 50% date is October 9, indicating even odds of a light frost around that time, while the median hard-frost date in fall is October 20. A hard frost at 28°F can injure plants that survive a 32°F light frost, making it the more critical temperature threshold. The period between the two 32°F 50% dates spans 162 days.

How to read the probabilities

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

  • Spring: "10% after May 11" 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 Toledo, IANumbered nearest stations: 1 — Marshalltown, IA — 18 mi; 2 — Belle Plaine, IA — 19 mi; 3 — Grinnell, IA — 23 mi; 4 — Grundy Center, IA — 25 mi; 5 — Vinton, IA — 31 mi.25 mi · 40 km1. Marshalltown, IA — 18 mi12. Belle Plaine, IA — 19 mi23. Grinnell, IA — 23 mi34. Grundy Center, IA — 25 mi45. Vinton, IA — 31 mi5
  1. Marshalltown, IA 18 mi (29 km)
  2. Belle Plaine, IA 19 mi (30 km)
  3. Grinnell, IA 23 mi (38 km)
  4. Grundy Center, IA 25 mi (39 km)
  5. Vinton, IA 31 mi (50 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: 42.0356, -92.5806.