Frost dates for 21275Baltimore, 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 18 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 21275 is matched to the NOAA station Md Sci Ctr Baltimore, MD, 1.1 km away, at 20 ft elevation (19 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 |
| Laurel 3 W, MD | 400 ft | Apr 5 | Nov 9 |
Frost dates near Baltimore
- Baltimore, MD 21203 · last Mar 24, first Nov 21
- Brooklyn, MD 21225 · last Mar 24, first Nov 21
- Halethorpe, MD 21227 · last Apr 10, first Oct 31
- Linthicum Heights, MD 21090 · last Apr 10, first Oct 31
- Curtis Bay, MD 21226 · last Apr 10, first Oct 31
- Catonsville, MD 21228 · last Apr 10, first Oct 31
- Gwynn Oak, MD 21207 · last Mar 24, first Nov 21
- Dundalk, MD 21222 · last Mar 24, first Nov 21
Frequently asked questions
- When is the last frost in Baltimore, MD?
- For ZIP code 21275, 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 21275?
- 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.