Frost dates for 21020Boring, MD
The average last spring frost in Boring is April 19 and the average first fall frost is October 25, giving a typical growing season of about 188 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 19
- Average first fall frost
- Oct 25
- Growing season
- 188 days
Safer after May 8 (1-in-10 risk)
Possible by Oct 8 (1-in-10 risk)
Last frost typically in 169 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 17 · May 2 · May 18 | Oct 1 · Oct 13 · Oct 27 | 162 days | 100% |
| Frost / freeze (32°F) | Apr 4 · Apr 19 · May 8 | Oct 8 · Oct 25 · Nov 7 | 188 days | 100% |
| Hard freeze (28°F) | Mar 22 · Apr 5 · Apr 21 | Oct 20 · Nov 4 · Nov 20 | 213 days | 100% |
Planting calendar for Boring
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 19 – May 25 |
| Tomatoes | Transplant outdoors | May 5 – Jul 5 |
| Peppers | Start seeds indoors | Mar 19 – Apr 19 |
| Peppers | Transplant outdoors | May 19 – Jun 19 |
| Eggplant | Start seeds indoors | Apr 5 – May 4 |
| Eggplant | Transplant outdoors | May 19 – Jun 19 |
| Cucumbers | Sow outdoors | May 19 – Jul 15 |
| Summer squash | Sow outdoors | May 5 – Jun 19 |
| Winter squash & pumpkins | Sow outdoors | May 19 – Jun 19 |
| Snap beans | Sow outdoors | May 5 – Aug 7 |
| Sweet corn | Sow outdoors | May 5 – Jul 5 |
| Watermelon & cantaloupe | Sow outdoors | May 19 – Jun 19 |
| Okra | Sow outdoors | May 12 – Jun 4 |
| Peas | Sow outdoors (spring) | Mar 19 – May 4 |
| Potatoes | Plant outdoors (spring) | Mar 19 – May 19 |
| Onions | Start seeds indoors (spring) | Feb 5 – Mar 4 |
| Onions | Transplant outdoors (spring) | Apr 5 – May 4 |
| Broccoli | Start seeds indoors (spring) | Mar 1 – Apr 4 |
| Broccoli | Transplant outdoors (spring) | Apr 5 – May 4 |
| Broccoli | Start seeds indoors (fall) | Jun 25 – Jul 5 |
| Broccoli | Transplant outdoors (fall) | Jul 25 – Aug 5 |
| Cabbage | Start seeds indoors (spring) | Feb 19 – Mar 19 |
| Cabbage | Transplant outdoors (spring) | Mar 19 – Apr 19 |
| Cabbage | Start seeds indoors (fall) | Jun 15 – Jul 15 |
| Cabbage | Transplant outdoors (fall) | Jul 15 – Aug 15 |
| Leaf lettuce | Sow outdoors (spring) | Mar 19 – Jun 4 |
| Leaf lettuce | Sow outdoors (fall) | Jul 15 – Aug 31 |
| Spinach | Sow outdoors (spring) | Mar 12 – Apr 25 |
| Spinach | Sow outdoors (fall) | Aug 1 – Sep 5 |
| Radishes | Sow outdoors (spring) | Mar 19 – May 9 |
| Radishes | Sow outdoors (fall) | Jul 15 – Sep 15 |
| Kale | Sow outdoors (spring) | Apr 5 – Apr 25 |
| Kale | Sow outdoors (fall) | Jul 8 – Aug 15 |
| Carrots | Sow outdoors (spring) | Apr 19 – Jun 4 |
| Carrots | Sow outdoors (fall) | Jun 15 – Jul 31 |
| Garlic | Plant outdoors (fall) | Oct 15 – Nov 15 |
Where these dates come from
ZIP code 21020 is matched to the NOAA station Millers 4 Ne, MD, 22 km away, at 860 ft elevation (237 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Millers 4 Ne, MD (used) | 860 ft | Apr 19 | Oct 25 |
| Cylburn, MD | 235 ft | Apr 2 | Nov 7 |
| Md Sci Ctr Baltimore, MD | 20 ft | Mar 24 | Nov 21 |
| Hanover 4 Sw, PA | 558 ft | Apr 24 | Oct 20 |
Frost dates near Boring
- Glyndon, MD 21071 · last Apr 19, first Oct 25
- Upperco, MD 21155 · last Apr 24, first Oct 20
- Butler, MD 21023 · last Apr 19, first Oct 25
- Reisterstown, MD 21136 · last Apr 19, first Oct 25
- Finksburg, MD 21048 · last Apr 24, first Oct 20
- Owings Mills, MD 21117 · last Apr 2, first Nov 7
- Sparks Glencoe, MD 21152 · last Apr 19, first Oct 25
- Hampstead, MD 21074 · last Apr 19, first Oct 25
Frequently asked questions
- When is the last frost in Boring, MD?
- For ZIP code 21020, the average last spring frost (32°F) is April 19, based on NOAA 1991-2020 climate normals for the Millers 4 Ne, MD weather station. There is a 1-in-10 chance of a frost after May 8.
- When is the first frost in Boring, MD?
- The average first fall frost (32°F) is October 25. There is a 1-in-10 chance of frost by October 8, so tender plants are at risk from that point on.
- How long is the growing season in 21020?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 188 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.