U.S. Frost Dates by Weather Station

NOAA station USC00409219 · Tennessee

Frost Dates for Union City, TN

NOAA weather station Union City (USC00409219), Tennessee · elevation 350 ft (107 m) · hardiness zone 7b*

  • Lower-risk planting dateafter April 19only 1 spring in 10 still has a frost later
  • Typical last frostApril 350% chance of a frost after it
  • Typical first fall frostOctober 2950% chance of a frost before it
  • Frost-free season208 daystypical year, 32°F
  • Hardiness zone7bcalculated*

The year at a glance

Frost season at Union City, TNSpring: a frost after March 18 in 9 years out of 10, after April 3 in half of the years, after April 19 in 1 year out of 10. Fall: the first frost comes before October 17 in 1 year out of 10, before October 29 in half of the years, before November 10 in 9 years out of 10. Typical frost-free season: 208 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 3First frost ~Oct 29Frost season at Union City, TNSpring: a frost after March 18 in 9 years out of 10, after April 3 in half of the years, after April 19 in 1 year out of 10. Fall: the first frost comes before October 17 in 1 year out of 10, before October 29 in half of the years, before November 10 in 9 years out of 10. Typical frost-free season: 208 days.JFMAMJJASONDLast frost ~Apr 3First frost ~Oct 29
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 19October 17
50% (typical)April 3October 29
90% (likely)March 18November 10
Frost-free season (32°F, 50% chance)
208 days
Hard frost (28°F), last in spring, 50% chance after
March 22
Hard frost (28°F), first in fall, 50% chance before
November 7

The last 15 years (2006–2020 normals)

Typical last frost April 3 (same as the 30-year normal), typical first fall frost October 29. Frost-free season 207 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 Union City: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 19, 20% April 14, 30% April 10, 40% April 6, 50% April 3, 60% March 31, 70% March 28, 80% March 24, 90% March 18. Observed last spring frost in recent years: 2021 April 21, 2022 April 2, 2023 March 19, 2024 March 20, 2025 March 22, 2026 March 19.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 19Apr 3Mar 182021: April 212022: April 22023: March 192024: March 202025: March 222026: March 19Fall at Union City: chance of a frost before this dateFall, chance of a frost before the date: 10% October 17, 20% October 20, 30% October 24, 40% October 26, 50% October 29, 60% October 31, 70% November 2, 80% November 5, 90% November 10. Observed first fall frost in recent years: 2021 November 4, 2022 October 17, 2023 October 30, 2024 October 17, 2025 November 10.Fall: first frostChance of a frost before this date10%50%90%Nov 1Oct 17Oct 29Nov 102021: November 42022: October 172023: October 302024: October 172025: November 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 21November 4
2022April 2October 17
2023March 19October 30
2024March 20October 17
2025March 22November 10
2026March 19season not over yet

What these dates mean

Setting out tender crops on the early spring date, March 18, carries a 90% chance of a light frost and is therefore a gamble for Union City growers. The 50% date is April 3, meaning there is an even chance of a light frost later than this date. The cautious approach uses the later April 19 date, which has only a 10% chance of a light frost, providing a lower-risk window for planting.

In the autumn, the 10% chance October 17 date marks the cautious point to finish harvesting tender crops, while the 50% date, October 29, signals an even chance of a light frost earlier than this date. A hard frost, defined at 28 °F, is more damaging than a light frost at 32 °F because it can kill plant tissue rather than merely chill it.

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 17" 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 Union City, TNNumbered nearest stations: 1 — Martin, TN — 10 mi; 2 — Murray, KY — 43 mi; 3 — Huntingdon, TN — 43 mi; 4 — Sikeston, MO — 47 mi; 5 — Paducah, KY — 49 mi.MOKYARIL25 mi · 40 km1. Martin, TN — 10 mi12. Murray, KY — 43 mi23. Huntingdon, TN — 43 mi34. Sikeston, MO — 47 mi45. Paducah, KY — 49 mi5
  1. Martin, TN 10 mi (16 km)
  2. Murray, KY 43 mi (69 km)
  3. Huntingdon, TN 43 mi (70 km)
  4. Sikeston, MO 47 mi (75 km)
  5. Paducah, KY 49 mi (79 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: 36.3925, -89.0317.