Baltimore, Maryland Frost Dates, Growing Season & Hardiness Zone

When is the last frost in Baltimore?

Expect the last 32°F night by Mar 24 in a typical year; 1 year in 10 still freezes after Apr 4. Cold 36°F nights (frost possible on plants) typically last longer, until around Apr 3. Hard freezes (28°F) typically end sooner, around Mar 11.

Planting between the typical date (Mar 24) and the safer 1-in-10 date (Apr 4) is a bet. Over those 11 days, let the 10-day forecast guide you.

The typical last 36°F night (frost possible on plants in low spots) comes around Apr 3, 10 days after the typical last 32°F night. On clear, calm nights, frost can form on leaves even when the thermometer reads above freezing.

Is it too early to plant in Baltimore?

Before Mar 24 the odds of another 32°F night are better than even; after Apr 4 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 Baltimore?

The typical first fall freeze (32°F) comes by Nov 21, but 1 year in 10 it shows up as early as Nov 7. Cold 36°F nights (frost possible on plants) typically start around Nov 10, and the first hard freeze (28°F) typically comes around Dec 5.

Fall plantings are timed backward from first frost: Nov 21 typically, or Nov 7 if you want a cushion. See the planting calendar for each crop's date.

How long is Baltimore's growing season?

A typical year in Baltimore has 244 days between the last spring and first fall 32°F nights. In about 1 year in 10, there are fewer than 224 days.

With a season this long, you can grow many crops twice: once in spring and again for fall.

The station averages 4,686 growing degree days (base 50°F) a year. That number measures how much heat crops have to grow on.

How does Baltimore'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 38 of them and shorter than in 16.

Growing degree days (base 50°F)

Annual normal: 4,686 GDD (NOAA flag R, 16 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 Baltimore? (USDA 2023)

Baltimore is in USDA zone 7b–8a on the 2023 map, which means an average coldest winter night of 5 to 15°F. Most of the city was 7b on the 2012 map, and 18 of 31 city ZIPs found in both tables 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 Baltimore'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. Baltimore'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 Baltimore frost dates differ between websites?

Some sources list Mar 29 for Baltimore. That's the 30%-risk date: about 3 years in 10 still see a 32°F night after it. We headline the 50% (median) date, Mar 24.

Apr 4 is the date we call 'safer': it's the 10%-risk date, with a 32°F night after it in only about 1 year in 10.

You may also see Apr 3. 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.

Sites also pick different weather stations. Within 25 miles of the city center, the 6 stations that meet our quality rules put the typical (50%) last 32°F frost anywhere from Mar 23 to Apr 10 (table below).

Which weather station is this based on?

Station

Maryland Science Center Baltimore (NOAA USW00093784, WBAN/ASOS-AWOS)

Distance

1.3 mi S of the city center

Elevation

20 ft; city center 39 ft (USGS), difference −19 ft

Record

NOAA completeness flag R, 19 of 30 years (1991–2020)

Confidence

Medium (rule)

Confidence: Medium. The station passes our quality rules but isn't an ideal match: 1.3 mi away, −19 ft elevation difference (NOAA flag R, 19 of 30 years).

Note: NOAA rates this station's frost statistics 'R' (representative). That means they use 19 of the 30 years in 1991–2020, with missing months filled in from surrounding stations. For comparison, the nearest station with a full 'S' (standard) record, Baltimore-Washington International Airport (10.0 mi away), has a typical last frost of Apr 10.

Baltimore planting dates at a glance

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

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

Frost dates near Baltimore

All Maryland cities

Frequently asked questions

What is the average last frost date in Baltimore?

Mar 24 is the median (50%) date for Baltimore's last 32°F night, from NOAA 1991–2020 normals at Maryland Science Center Baltimore. To play it safe, use Apr 4: only about 1 year in 10 has a freeze after it.

When is the first frost in Baltimore?

Typically by Nov 21 for the first 32°F night, though about 1 year in 10 it comes as early as Nov 7. The first 36°F night (frost possible on plants) typically shows up around Nov 10.

What growing zone is Baltimore, Maryland?

Baltimore is in USDA hardiness zone 7b–8a on the 2023 map. Most of the city was already 7b on the 2012 map, though 18 of 31 city ZIPs changed zone.

Is it too early to plant in Baltimore?

If it's before Mar 24, it's too early for frost-tender plants: another 32°F night is more likely than not. From Mar 24 to Apr 4, the risk falls from 50% to 10%. Cool-season crops such as peas and lettuce can be planted weeks earlier (see the planting calendar).

What temperature is a killing frost?

For tender crops like tomatoes, a light frost is a killing frost. CSU Extension calls 28–32°F a light frost and below 28°F a heavy frost. Our NOAA odds cover 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 quite. A 'freeze' means the air reached 32°F. 'Frost' is ice on surfaces, and it can form on calm, clear nights even when the air is a few degrees above freezing. So in Baltimore, the first 36°F night (frost possible on plants) typically comes around Nov 10, before the first 32°F night (Nov 21).

Download & sources

• Add Baltimore 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 USW00093784); 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.