Frost dates for 20855Derwood, MD
The average last spring frost in Derwood is April 1 and the average first fall frost is November 6, giving a typical growing season of about 219 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 1
- Average first fall frost
- Nov 6
- Growing season
- 219 days
Safer after Apr 15 (1-in-10 risk)
Possible by Oct 24 (1-in-10 risk)
First frost typically in 3 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 31 · Apr 16 · May 5 | Oct 12 · Oct 25 · Nov 7 | 192 days | 100% |
| Frost / freeze (32°F) | Mar 19 · Apr 1 · Apr 15 | Oct 24 · Nov 6 · Nov 21 | 219 days | 100% |
| Hard freeze (28°F) | Mar 5 · Mar 22 · Apr 4 | Nov 5 · Nov 19 · Dec 6 | 243 days | 100% |
Planting calendar for Derwood
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 | Mar 1 – May 7 |
| Tomatoes | Transplant outdoors | Apr 17 – Jul 17 |
| Peppers | Start seeds indoors | Mar 1 – Apr 1 |
| Peppers | Transplant outdoors | May 1 – Jun 1 |
| Eggplant | Start seeds indoors | Mar 18 – Apr 16 |
| Eggplant | Transplant outdoors | May 1 – Jun 1 |
| Cucumbers | Sow outdoors | May 1 – Jul 27 |
| Summer squash | Sow outdoors | Apr 17 – Jun 1 |
| Winter squash & pumpkins | Sow outdoors | May 1 – Jun 1 |
| Snap beans | Sow outdoors | Apr 17 – Aug 19 |
| Sweet corn | Sow outdoors | Apr 17 – Jul 17 |
| Watermelon & cantaloupe | Sow outdoors | May 1 – Jun 1 |
| Okra | Sow outdoors | Apr 24 – May 17 |
| Peas | Sow outdoors (spring) | Mar 1 – Apr 16 |
| Potatoes | Plant outdoors (spring) | Mar 1 – May 1 |
| Onions | Start seeds indoors (spring) | Jan 18 – Feb 14 |
| Onions | Transplant outdoors (spring) | Mar 18 – Apr 16 |
| Broccoli | Start seeds indoors (spring) | Feb 11 – Mar 17 |
| Broccoli | Transplant outdoors (spring) | Mar 18 – Apr 16 |
| Broccoli | Start seeds indoors (fall) | Jul 7 – Jul 17 |
| Broccoli | Transplant outdoors (fall) | Aug 6 – Aug 17 |
| Cabbage | Start seeds indoors (spring) | Feb 1 – Mar 1 |
| Cabbage | Transplant outdoors (spring) | Mar 1 – Apr 1 |
| Cabbage | Start seeds indoors (fall) | Jun 27 – Jul 27 |
| Cabbage | Transplant outdoors (fall) | Jul 27 – Aug 27 |
| Leaf lettuce | Sow outdoors (spring) | Mar 1 – May 17 |
| Leaf lettuce | Sow outdoors (fall) | Jul 27 – Sep 12 |
| Spinach | Sow outdoors (spring) | Feb 22 – Apr 7 |
| Spinach | Sow outdoors (fall) | Aug 13 – Sep 17 |
| Radishes | Sow outdoors (spring) | Mar 1 – Apr 21 |
| Radishes | Sow outdoors (fall) | Jul 27 – Sep 27 |
| Kale | Sow outdoors (spring) | Mar 18 – Apr 7 |
| Kale | Sow outdoors (fall) | Jul 20 – Aug 27 |
| Carrots | Sow outdoors (spring) | Apr 1 – May 17 |
| Carrots | Sow outdoors (fall) | Jun 27 – Aug 12 |
| Garlic | Plant outdoors (fall) | Oct 27 – Nov 27 |
Where these dates come from
ZIP code 20855 is matched to the NOAA station Rockville 1 Ne, MD, 3.7 km away, at 440 ft elevation (10 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Rockville 1 Ne, MD (used) | 440 ft | Apr 1 | Nov 6 |
| Damascus 3 Ssw, MD | 700 ft | Apr 14 | Oct 29 |
| Beltsville, MD | 145 ft | Apr 10 | Nov 1 |
| Dalecarlia Rsvr, MD | 150 ft | Apr 9 | Oct 31 |
Frost dates near Derwood
- Washington Grove, MD 20880 · last Apr 14, first Oct 29
- Gaithersburg, MD 20877 · last Apr 14, first Oct 29
- Bethesda, MD 20813 · last Apr 1, first Nov 6
- Rockville, MD 20848 · last Apr 1, first Nov 6
- Potomac, MD 20859 · last Apr 1, first Nov 6
- Germantown, MD 20875 · last Apr 1, first Nov 6
- Suburb Maryland Fac, MD 20897 · last Apr 1, first Nov 6
- Montgomery Village, MD 20886 · last Apr 14, first Oct 29
Frequently asked questions
- When is the last frost in Derwood, MD?
- For ZIP code 20855, the average last spring frost (32°F) is April 1, based on NOAA 1991-2020 climate normals for the Rockville 1 Ne, MD weather station. There is a 1-in-10 chance of a frost after April 15.
- When is the first frost in Derwood, MD?
- The average first fall frost (32°F) is November 6. There is a 1-in-10 chance of frost by October 24, so tender plants are at risk from that point on.
- How long is the growing season in 20855?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 219 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.