Washington, District of Columbia Frost Dates, Growing Season & Hardiness Zone

When is the last frost in Washington?

Expect the last 32°F night by Mar 29 in a typical year; 1 year in 10 still freezes after Apr 11. Cold 36°F nights (frost possible on plants) typically last longer, until around Apr 10. Hard freezes (28°F) typically end sooner, around Mar 17.

There are 13 days between the typical date (Mar 29) and the safer 1-in-10 date (Apr 11). Planting in that stretch is a gamble, so keep an eye on the 10-day forecast.

Cool nights hang on after the last freeze: the typical last 36°F night (frost possible on plants in low spots) is around Apr 10, 12 days later than the typical last 32°F night. Frost can form on leaves on clear, calm nights even with the thermometer above freezing.

Is it too early to plant in Washington?

Before Mar 29 the odds of another 32°F night are better than even; after Apr 11 they are about 1 in 10 or less.

Today's risk is computed in your browser from the same NOAA probability table, shown as the range between the two nearest NOAA probability levels.

When is the first frost in Washington?

Half of years get their first 32°F night by Nov 8. In 1 year out of 10, it arrives as early as Oct 26. The first 36°F night (frost possible on plants) typically comes around Oct 29, and the first 28°F hard freeze around Nov 20.

To time a fall crop, count back from the typical first frost (Nov 8) or the safer Oct 26. The planting calendar works it out crop by crop.

How long is Washington's growing season?

A typical year in Washington has 224 days between the last spring and first fall 32°F nights. In about 1 year in 10, there are fewer than 205 days.

That's enough time for most warm-season vegetables if they go in on time. Long-season crops do best started from transplants.

Growing degree days measure the heat available for crops to grow. The station averages 4,518 a year (base 50°F).

How does Washington's season compare?

Among the 56 U.S. cities with frost dates on this site, the typical frost-free season here is longer than in 33 of them and shorter than in 22.

Growing degree days (base 50°F)

Annual normal: 4,518 GDD (NOAA flag R, 21 years). Running total by the end of each month (sum of NOAA daily GDD normals, so the year-end total can differ slightly from the annual normal):

What growing zone is Washington? (USDA 2023)

The 2023 USDA map puts Washington in zone 7b–8a (5 to 15°F average coldest winter night); on the 2012 map, most of it was 7a. How the 54 ZIPs listed in both tables changed: 11 moved up a full zone and 43 moved up half a zone.

Zones: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 2026-10-08. Shown as published in the ZIP tables; this page does not show a zone map. Not the official USDA Plant Hardiness Zone Map (official map: planthardiness.ars.usda.gov).

Does the new zone change Washington's frost dates?

No. Hardiness zones are based only on the average coldest winter temperature. They say nothing about when spring and fall frosts happen. Washington's frost dates come from NOAA's 1991–2020 frost probabilities, which did not change with the 2023 zone map. Use your zone to pick perennials that will survive winter, and your frost dates to time planting.

Why do Washington frost dates differ between websites?

You may see Apr 3 given as Washington's last frost date. That's the 30%-risk date, meaning about 3 years in 10 still have a 32°F night after it. Our headline date is Mar 29, the 50% (median) date.

The 'safer' date, Apr 11, is the 10%-risk date. A 32°F night after it happens in only about 1 year in 10.

You may also see Apr 10. That's the 50% date for a 36°F night (frost possible on plants) rather than a 32°F freeze, so sites using 36°F as their cutoff list later dates.

Station choice is another reason dates differ. Our 11 qualifying stations within 25 miles of the city center range from Mar 24 to Apr 22 for the typical (50%) last 32°F frost (table below).

Which weather station is this based on?

Station

National Arboretum DC (NOAA USC00186350, COOP)

Distance

2.6 mi ENE of the city center

Elevation

50 ft; city center 56 ft (USGS), difference −6 ft

Record

NOAA completeness flag S, 29 of 30 years (1991–2020)

Confidence

High (rule)

Confidence: High. The station is 2.6 miles from the city center, only 6 ft different in elevation, and its frost statistics meet our completeness rule (NOAA flag S, 29 of 30 years).

Washington planting dates at a glance

Balanced dates use the 30%-risk last-frost date as the anchor. The Washington planting calendar has typical and safe dates, fall planting and a month-by-month list for 26 vegetables.

When to plant tomatoes in Washington · Fall planting dates for Washington

Frost dates near Washington

All District of Columbia cities

Frequently asked questions

What is the average last frost date in Washington?

The typical (median, 50%) last 32°F night in Washington is Mar 29, based on NOAA 1991–2020 normals at National Arboretum DC. For a safer target, use Apr 11; after that, only about 1 year in 10 still has a freeze.

When is the first frost in Washington?

Typically by Nov 8 for the first 32°F night, though about 1 year in 10 it comes as early as Oct 26. The first 36°F night (frost possible on plants) typically shows up around Oct 29.

What growing zone is Washington, District of Columbia?

Washington is in USDA hardiness zone 7b–8a on the current 2023 map. On the older 2012 map, most of the city was 7a, so older references may list that zone.

Is it too early to plant in Washington?

Before Mar 29, yes, for anything frost-tender. Until then, the odds of another 32°F night are better than even. The risk falls from 50% to 10% between Mar 29 and Apr 11. Peas, lettuce and other cool-season crops can go in weeks earlier; the planting calendar has dates.

What temperature is a killing frost?

A light frost is enough to kill tender crops such as tomatoes. CSU Extension describes 28–32°F as a light frost and anything below 28°F as a heavy frost. We report NOAA odds at three thresholds: 36°F (frost possible on plants), 32°F (freeze, our headline) and 28°F (hard freeze).

Is first frost the same as first freeze?

Not exactly. A freeze is about the air reaching 32°F. Frost is ice on surfaces, which can form on calm, clear nights while the air is still a few degrees above freezing. So in Washington, the first 36°F night (frost possible on plants) typically comes around Oct 29, ahead of the first 32°F night (Nov 8).

Download & sources

• Add Washington frost & planting dates to your calendar (.ics, 2027)
• Printable planting calendar (PDF)
• How these numbers are calculated

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal and daily normals, station USC00186350); USDA Plant Hardiness Zone ZIP tables 2023 and 2012 by the PRISM Group, Oregon State University; Census 2020 ZIP/place relationship file; USGS elevation. Long-term odds, not a forecast. Figures and sentences are generated from these data by fixed rules; see the methodology. Last updated 2026-10-08.