Frost dates for 20818Cabin John, MD
The average last spring frost in Cabin John is April 9 and the average first fall frost is October 31, giving a typical growing season of about 202 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 9
- Average first fall frost
- Oct 31
- Growing season
- 202 days
Safer after Apr 26 (1-in-10 risk)
Possible by Oct 16 (1-in-10 risk)
Last frost typically in 157 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) | Apr 8 · Apr 23 · May 10 | Oct 7 · Oct 20 · Nov 2 | 179 days | 100% |
| Frost / freeze (32°F) | Mar 27 · Apr 9 · Apr 26 | Oct 16 · Oct 31 · Nov 13 | 202 days | 100% |
| Hard freeze (28°F) | Mar 12 · Mar 30 · Apr 12 | Oct 29 · Nov 9 · Nov 27 | 226 days | 100% |
Planting calendar for Cabin John
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 9 – May 15 |
| Tomatoes | Transplant outdoors | Apr 25 – Jul 11 |
| Peppers | Start seeds indoors | Mar 9 – Apr 9 |
| Peppers | Transplant outdoors | May 9 – Jun 9 |
| Eggplant | Start seeds indoors | Mar 26 – Apr 24 |
| Eggplant | Transplant outdoors | May 9 – Jun 9 |
| Cucumbers | Sow outdoors | May 9 – Jul 21 |
| Summer squash | Sow outdoors | Apr 25 – Jun 9 |
| Winter squash & pumpkins | Sow outdoors | May 9 – Jun 9 |
| Snap beans | Sow outdoors | Apr 25 – Aug 13 |
| Sweet corn | Sow outdoors | Apr 25 – Jul 11 |
| Watermelon & cantaloupe | Sow outdoors | May 9 – Jun 9 |
| Okra | Sow outdoors | May 2 – May 25 |
| Peas | Sow outdoors (spring) | Mar 9 – Apr 24 |
| Potatoes | Plant outdoors (spring) | Mar 9 – May 9 |
| Onions | Start seeds indoors (spring) | Jan 26 – Feb 22 |
| Onions | Transplant outdoors (spring) | Mar 26 – Apr 24 |
| Broccoli | Start seeds indoors (spring) | Feb 19 – Mar 25 |
| Broccoli | Transplant outdoors (spring) | Mar 26 – Apr 24 |
| Broccoli | Start seeds indoors (fall) | Jul 1 – Jul 11 |
| Broccoli | Transplant outdoors (fall) | Jul 31 – Aug 11 |
| Cabbage | Start seeds indoors (spring) | Feb 9 – Mar 9 |
| Cabbage | Transplant outdoors (spring) | Mar 9 – Apr 9 |
| Cabbage | Start seeds indoors (fall) | Jun 21 – Jul 21 |
| Cabbage | Transplant outdoors (fall) | Jul 21 – Aug 21 |
| Leaf lettuce | Sow outdoors (spring) | Mar 9 – May 25 |
| Leaf lettuce | Sow outdoors (fall) | Jul 21 – Sep 6 |
| Spinach | Sow outdoors (spring) | Mar 2 – Apr 15 |
| Spinach | Sow outdoors (fall) | Aug 7 – Sep 11 |
| Radishes | Sow outdoors (spring) | Mar 9 – Apr 29 |
| Radishes | Sow outdoors (fall) | Jul 21 – Sep 21 |
| Kale | Sow outdoors (spring) | Mar 26 – Apr 15 |
| Kale | Sow outdoors (fall) | Jul 14 – Aug 21 |
| Carrots | Sow outdoors (spring) | Apr 9 – May 25 |
| Carrots | Sow outdoors (fall) | Jun 21 – Aug 6 |
| Garlic | Plant outdoors (fall) | Oct 21 – Nov 21 |
Where these dates come from
ZIP code 20818 is matched to the NOAA station Dalecarlia Rsvr, MD, 5.6 km away, at 150 ft elevation (8 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Dalecarlia Rsvr, MD (used) | 150 ft | Apr 9 | Oct 31 |
| Rockville 1 Ne, MD | 440 ft | Apr 1 | Nov 6 |
| Vienna, VA | 418 ft | Apr 14 | Oct 29 |
| Washington Reagan Ap, VA | 10 ft | Mar 24 | Nov 18 |
Frost dates near Cabin John
- Glen Echo, MD 20812 · last Apr 9, first Oct 31
- Bethesda, MD 20817 · last Apr 9, first Oct 31
- Mc Lean, VA 22101 · last Apr 9, first Oct 31
- Greenway, VA 22067 · last Apr 14, first Oct 29
- Chevy Chase, MD 20815 · last Apr 9, first Oct 31
- Washington, DC 20016 · last Apr 9, first Oct 31
- Potomac, MD 20854 · last Apr 14, first Oct 29
- Arlington, VA 22207 · last Apr 14, first Oct 29
Frequently asked questions
- When is the last frost in Cabin John, MD?
- For ZIP code 20818, the average last spring frost (32°F) is April 9, based on NOAA 1991-2020 climate normals for the Dalecarlia Rsvr, MD weather station. There is a 1-in-10 chance of a frost after April 26.
- When is the first frost in Cabin John, MD?
- The average first fall frost (32°F) is October 31. There is a 1-in-10 chance of frost by October 16, so tender plants are at risk from that point on.
- How long is the growing season in 20818?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 202 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.