U.S. Frost Dates by Weather Station

NOAA station USC00473058 · Wisconsin

Frost Dates for Germantown, WI

NOAA weather station Germantown (USC00473058), Wisconsin · elevation 850 ft (259 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 25only 1 spring in 10 still has a frost later
  • Typical last frostMay 650% chance of a frost after it
  • Typical first fall frostOctober 850% chance of a frost before it
  • Frost-free season154 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Germantown, WISpring: a frost after April 22 in 9 years out of 10, after May 6 in half of the years, after May 25 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 8 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 154 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 6First frost ~Oct 8Frost season at Germantown, WISpring: a frost after April 22 in 9 years out of 10, after May 6 in half of the years, after May 25 in 1 year out of 10. Fall: the first frost comes before September 26 in 1 year out of 10, before October 8 in half of the years, before October 24 in 9 years out of 10. Typical frost-free season: 154 days.JFMAMJJASONDLast frost ~May 6First frost ~Oct 8
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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 25September 26
50% (typical)May 6October 8
90% (likely)April 22October 24
Frost-free season (32°F, 50% chance)
154 days
Hard frost (28°F), last in spring, 50% chance after
April 24
Hard frost (28°F), first in fall, 50% chance before
October 20

The last 15 years (2006–2020 normals)

Typical last frost May 1 (5 days earlier than the 30-year normal), typical first fall frost October 11 (3 days later). Frost-free season 160 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 Germantown: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 25, 20% May 19, 30% May 14, 40% May 10, 50% May 6, 60% May 2, 70% April 30, 80% April 26, 90% April 22. Observed last spring frost in recent years: 2021 May 12, 2022 May 5, 2023 April 28, 2024 April 26, 2025 May 9, 2026 May 9.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 25May 6Apr 222021: May 122022: May 52023: April 282024: April 262025: May 92026: May 9Fall at Germantown: 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 5, 50% October 8, 60% October 11, 70% October 14, 80% October 18, 90% October 24. Observed first fall frost in recent years: 2021 October 24, 2022 September 29, 2023 October 17, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 26Oct 8Oct 242021: October 242022: September 292023: October 172024: October 162025: October 24
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 12October 24
2022May 5September 29
2023April 28October 17
2024April 26October 16
2025May 9October 24
2026May 9season not over yet

What these dates mean

The 154 days between the 50% dates in Germantown frame the period when a light frost is equally likely to appear later or earlier. In spring the median light-frost date is May 6, and in fall the median light-frost date is October 8. These dates are not frost dates themselves; they simply split the 30-year record at the 50 % probability point. The hard-frost 50% dates are April 24 and October 20, marking the middle of the record for temperatures that reach 28 °F.

For a cautious planting schedule, gardeners should wait until the May 25 light-frost date, which carries only a 10 % chance of a frost occurring later, before setting out tender crops. In the harvest season the comparable cautious date is September 26, when there is only a 10 % chance that a light frost has already arrived, signaling when to finish harvesting tender crops.

A hard frost matters more than a light frost because temperatures of 28 °F can damage plant tissue that survives a 32 °F event.

How to read the probabilities

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

  • Spring: "10% after May 25" 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 Germantown, WINumbered nearest stations: 1 — near Wauwatosa, WI — 12 mi; 2 — Hartford, WI — 16 mi; 3 — Oconomowoc, WI — 21 mi; 4 — near Milwaukee, WI — 22 mi; 5 — Horicon, WI — 29 mi.WI25 mi · 40 km1. near Wauwatosa, WI — 12 mi12. Hartford, WI — 16 mi23. Oconomowoc, WI — 21 mi34. near Milwaukee, WI — 22 mi45. Horicon, WI — 29 mi5
  1. near Wauwatosa, WI 12 mi (20 km)
  2. Hartford, WI 16 mi (26 km)
  3. Oconomowoc, WI 21 mi (35 km)
  4. near Milwaukee, WI 22 mi (36 km)
  5. Horicon, WI 29 mi (47 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: 43.2389, -88.1222.