U.S. Frost Dates by Weather Station

NOAA station USC00407359 · Tennessee

Frost Dates for Portland, TN

NOAA weather station Portland Sewage Plant (USC00407359), Tennessee · elevation 794 ft (242 m) · hardiness zone 7b*

  • Lower-risk planting dateafter April 19only 1 spring in 10 still has a frost later
  • Typical last frostApril 550% chance of a frost after it
  • Typical first fall frostNovember 150% chance of a frost before it
  • Frost-free season210 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Portland, TNSpring: a frost after March 21 in 9 years out of 10, after April 5 in half of the years, after April 19 in 1 year out of 10. Fall: the first frost comes before October 21 in 1 year out of 10, before November 1 in half of the years, before November 14 in 9 years out of 10. Typical frost-free season: 210 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 5First frost ~Nov 1Frost season at Portland, TNSpring: a frost after March 21 in 9 years out of 10, after April 5 in half of the years, after April 19 in 1 year out of 10. Fall: the first frost comes before October 21 in 1 year out of 10, before November 1 in half of the years, before November 14 in 9 years out of 10. Typical frost-free season: 210 days.JFMAMJJASONDLast frost ~Apr 5First frost ~Nov 1
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 19October 21
50% (typical)April 5November 1
90% (likely)March 21November 14
Frost-free season (32°F, 50% chance)
210 days
Hard frost (28°F), last in spring, 50% chance after
March 26
Hard frost (28°F), first in fall, 50% chance before
November 11

The last 15 years (2006–2020 normals)

Typical last frost April 3 (2 days earlier than the 30-year normal), typical first fall frost November 1. Frost-free season 213 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 Portland: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 19, 20% April 13, 30% April 10, 40% April 7, 50% April 5, 60% April 1, 70% March 30, 80% March 27, 90% March 21. Observed last spring frost in recent years: 2021 May 14, 2022 April 28, 2023 March 29, 2024 April 6, 2025 April 10, 2026 March 18.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 19Apr 5Mar 212021: May 142022: April 282023: March 292024: April 62025: April 102026: March 18Fall at Portland: chance of a frost before this dateFall, chance of a frost before the date: 10% October 21, 20% October 24, 30% October 27, 40% October 30, 50% November 1, 60% November 3, 70% November 5, 80% November 9, 90% November 14. Observed first fall frost in recent years: 2022 October 18, 2023 October 31, 2024 November 29, 2025 November 3.Fall: first frostChance of a frost before this date10%50%90%Nov 1Dec 1Oct 21Nov 1Nov 142022: October 182023: October 312024: November 292025: November 3
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 14incomplete record
2022April 28October 18
2023March 29October 31
2024April 6November 29
2025April 10November 3
2026March 18season not over yet

What these dates mean

April 19 is the cautious spring date for light frost (32 °F) in Portland. With only a 10 % chance of a frost later than that day, a gardener can plan to set out tender crops after April 19 with relatively low risk.

The 50 % light-frost dates are April 5 and November 1; there is a 50 % chance of a light frost later than April 5 and a 50 % chance of a light frost earlier than November 1. These dates mark the point where a frost is equally likely to have occurred or not. The cautious fall date is October 21, when the chance of a frost earlier than that day is just 10 %, allowing the final harvest of tender crops. The 50 % hard-frost dates are March 26 and November 11; hard frost at 28 °F can injure plants that would survive a 32 °F light frost. The record spans 27 years, and the two 32 °F 50 % dates are 210 days apart.

How to read the probabilities

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

  • Spring: "10% after April 19" 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 21" 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 Portland, TNNumbered nearest stations: 1 — Springfield, TN — 19 mi; 2 — Scottsville, KY — 20 mi; 3 — near Green Hill, TN — 24 mi; 4 — near Bowling Green, KY — 27 mi; 5 — Barren River Lake, KY — 31 mi.25 mi · 40 km1. Springfield, TN — 19 mi12. Scottsville, KY — 20 mi23. near Green Hill, TN — 24 mi34. near Bowling Green, KY — 27 mi45. Barren River Lake, KY — 31 mi5
  1. Springfield, TN 19 mi (31 km)
  2. Scottsville, KY 20 mi (32 km)
  3. near Green Hill, TN 24 mi (38 km)
  4. near Bowling Green, KY 27 mi (43 km)
  5. Barren River Lake, KY 31 mi (50 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: 36.5878, -86.5258.