Frost dates for 21239Baltimore, MD
The average last spring frost in Baltimore is March 24 and the average first fall frost is November 21, giving a typical growing season of about 244 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 24
- Average first fall frost
- Nov 21
- Growing season
- 244 days
Safer after Apr 4 (1-in-10 risk)
Possible by Nov 7 (1-in-10 risk)
First frost typically in 19 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Mar 22 · Apr 3 · Apr 15 | Oct 29 · Nov 10 · Nov 24 | 221 days | 100% |
| Frost / freeze (32°F) | Mar 8 · Mar 24 · Apr 4 | Nov 7 · Nov 21 · Dec 8 | 244 days | 100% |
| Hard freeze (28°F) | Feb 24 · Mar 11 · Mar 26 | Nov 18 · Dec 5 · Dec 25 | 270 days | 100% |
Planting calendar for Baltimore
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Feb 21 – Apr 29 |
| Tomatoes | Transplant outdoors | Apr 9 – Aug 1 |
| Peppers | Start seeds indoors | Feb 21 – Mar 24 |
| Peppers | Transplant outdoors | Apr 23 – May 24 |
| Eggplant | Start seeds indoors | Mar 10 – Apr 8 |
| Eggplant | Transplant outdoors | Apr 23 – May 24 |
| Cucumbers | Sow outdoors | Apr 23 – Aug 11 |
| Summer squash | Sow outdoors | Apr 9 – May 24 |
| Winter squash & pumpkins | Sow outdoors | Apr 23 – May 24 |
| Snap beans | Sow outdoors | Apr 9 – Sep 3 |
| Sweet corn | Sow outdoors | Apr 9 – Aug 1 |
| Watermelon & cantaloupe | Sow outdoors | Apr 23 – May 24 |
| Okra | Sow outdoors | Apr 16 – May 9 |
| Peas | Sow outdoors (spring) | Feb 21 – Apr 8 |
| Potatoes | Plant outdoors (spring) | Feb 21 – Apr 23 |
| Onions | Start seeds indoors (spring) | Jan 10 – Feb 6 |
| Onions | Transplant outdoors (spring) | Mar 10 – Apr 8 |
| Broccoli | Start seeds indoors (spring) | Feb 3 – Mar 9 |
| Broccoli | Transplant outdoors (spring) | Mar 10 – Apr 8 |
| Broccoli | Start seeds indoors (fall) | Jul 22 – Aug 1 |
| Broccoli | Transplant outdoors (fall) | Aug 21 – Sep 1 |
| Cabbage | Start seeds indoors (spring) | Jan 24 – Feb 21 |
| Cabbage | Transplant outdoors (spring) | Feb 21 – Mar 24 |
| Cabbage | Start seeds indoors (fall) | Jul 12 – Aug 11 |
| Cabbage | Transplant outdoors (fall) | Aug 11 – Sep 11 |
| Leaf lettuce | Sow outdoors (spring) | Feb 21 – May 9 |
| Leaf lettuce | Sow outdoors (fall) | Aug 11 – Sep 27 |
| Spinach | Sow outdoors (spring) | Feb 14 – Mar 30 |
| Spinach | Sow outdoors (fall) | Aug 28 – Oct 2 |
| Radishes | Sow outdoors (spring) | Feb 21 – Apr 13 |
| Radishes | Sow outdoors (fall) | Aug 11 – Oct 12 |
| Kale | Sow outdoors (spring) | Mar 10 – Mar 30 |
| Kale | Sow outdoors (fall) | Aug 4 – Sep 11 |
| Carrots | Sow outdoors (spring) | Mar 24 – May 9 |
| Carrots | Sow outdoors (fall) | Jul 12 – Aug 27 |
| Garlic | Plant outdoors (fall) | Nov 11 – Dec 12 |
Where these dates come from
ZIP code 21239 is matched to the NOAA station Md Sci Ctr Baltimore, MD, 9 km away, at 20 ft elevation (351 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Md Sci Ctr Baltimore, MD (used) | 20 ft | Mar 24 | Nov 21 |
| Cylburn, MD | 235 ft | Apr 2 | Nov 7 |
| Baltimore Wash Intl Ap, MD | 156 ft | Apr 10 | Oct 31 |
| Aberdeen Phillips Fld, MD | 57 ft | Apr 10 | Oct 30 |
Frost dates near Baltimore
- Baltimore, MD 21212 · last Mar 24, first Nov 21
- Towson, MD 21252 · last Apr 2, first Nov 7
- Parkville, MD 21234 · last Mar 24, first Nov 21
- Riderwood, MD 21139 · last Apr 2, first Nov 7
- Rosedale, MD 21237 · last Mar 24, first Nov 21
- Brooklandville, MD 21022 · last Apr 2, first Nov 7
- Lutherville Timonium, MD 21094 · last Apr 2, first Nov 7
- Nottingham, MD 21236 · last Mar 24, first Nov 21
Frequently asked questions
- When is the last frost in Baltimore, MD?
- For ZIP code 21239, the average last spring frost (32°F) is March 24, based on NOAA 1991-2020 climate normals for the Md Sci Ctr Baltimore, MD weather station. There is a 1-in-10 chance of a frost after April 4.
- When is the first frost in Baltimore, MD?
- The average first fall frost (32°F) is November 21. There is a 1-in-10 chance of frost by November 7, so tender plants are at risk from that point on.
- How long is the growing season in 21239?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 244 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.