U.S. Frost Dates by Weather Station

NOAA station USC00206300 · Michigan

Frost Dates for Owosso, MI

NOAA weather station Owosso WWTP (USC00206300), Michigan · elevation 730 ft (223 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 17only 1 spring in 10 still has a frost later
  • Typical last frostMay 150% chance of a frost after it
  • Typical first fall frostOctober 1550% chance of a frost before it
  • Frost-free season164 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Owosso, MISpring: a frost after April 17 in 9 years out of 10, after May 1 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 15 in half of the years, before October 30 in 9 years out of 10. Typical frost-free season: 164 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 1First frost ~Oct 15Frost season at Owosso, MISpring: a frost after April 17 in 9 years out of 10, after May 1 in half of the years, after May 17 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 15 in half of the years, before October 30 in 9 years out of 10. Typical frost-free season: 164 days.JFMAMJJASONDLast frost ~May 1First frost ~Oct 15
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 17October 1
50% (typical)May 1October 15
90% (likely)April 17October 30
Frost-free season (32°F, 50% chance)
164 days
Hard frost (28°F), last in spring, 50% chance after
April 20
Hard frost (28°F), first in fall, 50% chance before
October 28

The last 15 years (2006–2020 normals)

Typical last frost May 1 (same as the 30-year normal), typical first fall frost October 19 (4 days later). Frost-free season 170 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 Owosso: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 17, 20% May 11, 30% May 7, 40% May 4, 50% May 1, 60% April 29, 70% April 26, 80% April 22, 90% April 17. Observed last spring frost in recent years: 2021 May 13, 2022 April 30, 2023 April 27, 2024 April 26, 2025 May 10.Spring: last frostChance of a frost after this date10%50%90%May 1May 17May 1Apr 172021: May 132022: April 302023: April 272024: April 262025: May 10Fall at Owosso: chance of a frost before this dateFall, chance of a frost before the date: 10% October 1, 20% October 5, 30% October 8, 40% October 12, 50% October 15, 60% October 17, 70% October 20, 80% October 24, 90% October 30. Observed first fall frost in recent years: 2021 November 3, 2022 October 8, 2023 October 23, 2024 October 25.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 1Oct 15Oct 302021: November 32022: October 82023: October 232024: October 25
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 13November 3
2022April 30October 8
2023April 27October 23
2024April 26October 25
2025May 10incomplete record
2026incomplete recordseason not over yet

What these dates mean

Setting out tender crops on April 17 in Owosso is a gamble, because there is a 90% chance of a light frost later than that date. The cautious alternative is May 17, when the chance of a frost later than the date drops to 10%, making it the preferred day for planting tender varieties. For the fall harvest, the cautious date is October 1, with only a 10% chance of a frost earlier than that date.

The 50% dates represent the point at which frost is equally likely to have occurred or not. For light frost the median dates are May 1 in spring and October 15 in fall; for hard frost the median dates are April 20 in spring and October 28 in fall. Gardeners can use these dates to gauge the midpoint of the frost risk window, noting that the two 32 °F 50% dates are 164 days apart over the 26-year record.

A hard frost at 28 °F can injure plants that would survive a light frost at 32 °F, so the hard-frost dates are especially relevant for protecting tender crops.

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 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 Owosso, MINumbered nearest stations: 1 — near Lansing, MI — 26 mi; 2 — near Saginaw, MI — 36 mi; 3 — Midland, MI — 41 mi; 4 — Charlotte, MI — 46 mi; 5 — near Jackson, MI — 54 mi.MI25 mi · 40 km1. near Lansing, MI — 26 mi12. near Saginaw, MI — 36 mi23. Midland, MI — 41 mi34. Charlotte, MI — 46 mi45. near Jackson, MI — 54 mi5
  1. near Lansing, MI 26 mi (42 km)
  2. near Saginaw, MI 36 mi (58 km)
  3. Midland, MI 41 mi (66 km)
  4. Charlotte, MI 46 mi (74 km)
  5. near Jackson, MI 54 mi (87 km)

Sources

* Hardiness zone 6a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 43.0161, -84.18.