U.S. Frost Dates by Weather Station

NOAA station USC00135992 · Iowa

Frost Dates for Newton, IA

NOAA weather station Newton (USC00135992), Iowa · elevation 960 ft (293 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 4only 1 spring in 10 still has a frost later
  • Typical last frostApril 2250% chance of a frost after it
  • Typical first fall frostOctober 1750% chance of a frost before it
  • Frost-free season174 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Newton, IASpring: a frost after April 8 in 9 years out of 10, after April 22 in half of the years, after May 4 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 17 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 174 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 22First frost ~Oct 17Frost season at Newton, IASpring: a frost after April 8 in 9 years out of 10, after April 22 in half of the years, after May 4 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 17 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 174 days.JFMAMJJASONDLast frost ~Apr 22First frost ~Oct 17
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 4October 1
50% (typical)April 22October 17
90% (likely)April 8October 28
Frost-free season (32°F, 50% chance)
174 days
Hard frost (28°F), last in spring, 50% chance after
April 12
Hard frost (28°F), first in fall, 50% chance before
October 26

The last 15 years (2006–2020 normals)

Typical last frost April 21 (1 day earlier than the 30-year normal), typical first fall frost October 20 (3 days later). Frost-free season 179 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 Newton: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 4, 20% May 1, 30% April 28, 40% April 25, 50% April 22, 60% April 19, 70% April 16, 80% April 13, 90% April 8. Observed last spring frost in recent years: 2021 April 25, 2022 April 27, 2023 April 25.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 4Apr 22Apr 82021: April 252022: April 272023: April 25Fall at Newton: chance of a frost before this dateFall, chance of a frost before the date: 10% October 1, 20% October 6, 30% October 11, 40% October 13, 50% October 17, 60% October 19, 70% October 22, 80% October 25, 90% October 28. Observed first fall frost in recent years: 2021 October 23, 2022 October 8, 2023 October 10.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 1Oct 17Oct 282021: October 232022: October 82023: October 10
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 25October 23
2022April 27October 8
2023April 25October 10
2024incomplete recordno data
2025no datano data
2026no dataseason not over yet

What these dates mean

May 4 is the cautious spring date for tender crops in Newton, carrying only a 10 % chance that a light frost will occur later; gardeners can plan to set out those sensitive plants after this date with relatively low risk.

The 50% dates—April 22 in spring and October 17 in fall—represent the median point where a light frost has an even chance of occurring later (spring) or earlier (fall). For hard frost the median dates are April 12 and October 26; a hard frost at 28 °F can damage or kill plants that would survive a 32 °F light frost, making it a more critical threshold.

In the fall the cautious date is October 1, when there is only a 10 % chance that a light frost has already arrived, allowing gardeners to finish harvesting tender crops with confidence.

How to read the probabilities

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

  • Spring: "10% after May 4" 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 October 1" 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 Newton, IANumbered nearest stations: 1 — Grinnell, IA — 14 mi; 2 — Marshalltown, IA — 25 mi; 3 — Ankeny, IA — 32 mi; 4 — Toledo, IA — 32 mi; 5 — Oskaloosa, IA — 33 mi.25 mi · 40 km1. Grinnell, IA — 14 mi12. Marshalltown, IA — 25 mi23. Ankeny, IA — 32 mi34. Toledo, IA — 32 mi45. Oskaloosa, IA — 33 mi5
  1. Grinnell, IA 14 mi (23 km)
  2. Marshalltown, IA 25 mi (40 km)
  3. Ankeny, IA 32 mi (52 km)
  4. Toledo, IA 32 mi (52 km)
  5. Oskaloosa, IA 33 mi (54 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: 41.7117, -93.0297.