U.S. Frost Dates by Weather Station

NOAA station USC00072730 · Delaware

Frost Dates for Dover, DE

NOAA weather station Dover (USC00072730), Delaware · elevation 30 ft (9 m) · hardiness zone 7b*

  • Lower-risk planting dateafter April 17only 1 spring in 10 still has a frost later
  • Typical last frostApril 450% chance of a frost after it
  • Typical first fall frostNovember 450% chance of a frost before it
  • Frost-free season214 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Dover, DESpring: a frost after March 22 in 9 years out of 10, after April 4 in half of the years, after April 17 in 1 year out of 10. Fall: the first frost comes before October 23 in 1 year out of 10, before November 4 in half of the years, before November 18 in 9 years out of 10. Typical frost-free season: 214 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 4First frost ~Nov 4Frost season at Dover, DESpring: a frost after March 22 in 9 years out of 10, after April 4 in half of the years, after April 17 in 1 year out of 10. Fall: the first frost comes before October 23 in 1 year out of 10, before November 4 in half of the years, before November 18 in 9 years out of 10. Typical frost-free season: 214 days.JFMAMJJASONDLast frost ~Apr 4First frost ~Nov 4
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)April 17October 23
50% (typical)April 4November 4
90% (likely)March 22November 18
Frost-free season (32°F, 50% chance)
214 days
Hard frost (28°F), last in spring, 50% chance after
March 25
Hard frost (28°F), first in fall, 50% chance before
November 16

The last 15 years (2006–2020 normals)

Typical last frost April 4 (same as the 30-year normal), typical first fall frost November 6 (2 days later). Frost-free season 216 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 Dover: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 17, 20% April 12, 30% April 9, 40% April 6, 50% April 4, 60% April 1, 70% March 31, 80% March 28, 90% March 22. Observed last spring frost in recent years: 2022 March 29, 2023 March 21, 2024 March 25, 2025 March 10, 2026 March 29.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 17Apr 4Mar 222022: March 292023: March 212024: March 252025: March 102026: March 29Fall at Dover: chance of a frost before this dateFall, chance of a frost before the date: 10% October 23, 20% October 28, 30% October 31, 40% November 2, 50% November 4, 60% November 6, 70% November 9, 80% November 13, 90% November 18. Observed first fall frost in recent years: 2022 November 18, 2023 November 2, 2024 November 27, 2025 November 18.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 23Nov 4Nov 182022: November 182023: November 22024: November 272025: November 18
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
2021no dataincomplete record
2022March 29November 18
2023March 21November 2
2024March 25November 27
2025March 10November 18
2026March 29season not over yet

What these dates mean

April 17 is the cautious spring date for Dover, offering only a 10 % chance that a light frost will occur later and allowing a gardener to set out tender crops with minimal risk. The 50% date, April 4, indicates a 50 % chance of a frost later than this date, while March 25 is the 50% hard-frost date in spring.

In fall, October 23 is the cautious date, carrying a 10 % chance that a light frost has arrived earlier and giving a gardener a reliable point to finish harvesting tender crops. The 50% date, November 4, signals a 50 % chance of a frost earlier than this date, and November 16 is the 50% hard-frost date in fall. A hard frost at 28 °F can damage plants that survive a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after April 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 23" 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 Dover, DENumbered nearest stations: 1 — Millville, NJ — 28 mi; 2 — Seabrook Farms, NJ — 28 mi; 3 — Cape May, NJ — 33 mi; 4 — near Wilmington Manor, DE — 37 mi; 5 — Estell Manor, NJ — 40 mi.MDNJPADE25 mi · 40 km1. Millville, NJ — 28 mi12. Seabrook Farms, NJ — 28 mi23. Cape May, NJ — 33 mi34. near Wilmington Manor, DE — 37 mi45. Estell Manor, NJ — 40 mi5
  1. Millville, NJ 28 mi (45 km)
  2. Seabrook Farms, NJ 28 mi (45 km)
  3. Cape May, NJ 33 mi (54 km)
  4. near Wilmington Manor, DE 37 mi (59 km)
  5. Estell Manor, NJ 40 mi (64 km)

Sources

* Hardiness zone 7b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 39.1467, -75.5056.