Frost dates for 20830Olney, MD
The average last spring frost in Olney is April 5 and the average first fall frost is November 9, giving a typical growing season of about 218 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 5
- Average first fall frost
- Nov 9
- Growing season
- 218 days
Safer after Apr 19 (1-in-10 risk)
Possible by Oct 27 (1-in-10 risk)
First frost typically in 6 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 2 · Apr 17 · May 2 | Oct 16 · Oct 29 · Nov 11 | 194 days | 100% |
| Frost / freeze (32°F) | Mar 21 · Apr 5 · Apr 19 | Oct 27 · Nov 9 · Nov 24 | 218 days | 100% |
| Hard freeze (28°F) | Mar 10 · Mar 25 · Apr 8 | Nov 5 · Nov 21 · Dec 8 | 242 days | 100% |
Planting calendar for Olney
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 5 – May 11 |
| Tomatoes | Transplant outdoors | Apr 21 – Jul 20 |
| Peppers | Start seeds indoors | Mar 5 – Apr 5 |
| Peppers | Transplant outdoors | May 5 – Jun 5 |
| Eggplant | Start seeds indoors | Mar 22 – Apr 20 |
| Eggplant | Transplant outdoors | May 5 – Jun 5 |
| Cucumbers | Sow outdoors | May 5 – Jul 30 |
| Summer squash | Sow outdoors | Apr 21 – Jun 5 |
| Winter squash & pumpkins | Sow outdoors | May 5 – Jun 5 |
| Snap beans | Sow outdoors | Apr 21 – Aug 22 |
| Sweet corn | Sow outdoors | Apr 21 – Jul 20 |
| Watermelon & cantaloupe | Sow outdoors | May 5 – Jun 5 |
| Okra | Sow outdoors | Apr 28 – May 21 |
| Peas | Sow outdoors (spring) | Mar 5 – Apr 20 |
| Potatoes | Plant outdoors (spring) | Mar 5 – May 5 |
| Onions | Start seeds indoors (spring) | Jan 22 – Feb 18 |
| Onions | Transplant outdoors (spring) | Mar 22 – Apr 20 |
| Broccoli | Start seeds indoors (spring) | Feb 15 – Mar 21 |
| Broccoli | Transplant outdoors (spring) | Mar 22 – Apr 20 |
| Broccoli | Start seeds indoors (fall) | Jul 10 – Jul 20 |
| Broccoli | Transplant outdoors (fall) | Aug 9 – Aug 20 |
| Cabbage | Start seeds indoors (spring) | Feb 5 – Mar 5 |
| Cabbage | Transplant outdoors (spring) | Mar 5 – Apr 5 |
| Cabbage | Start seeds indoors (fall) | Jun 30 – Jul 30 |
| Cabbage | Transplant outdoors (fall) | Jul 30 – Aug 30 |
| Leaf lettuce | Sow outdoors (spring) | Mar 5 – May 21 |
| Leaf lettuce | Sow outdoors (fall) | Jul 30 – Sep 15 |
| Spinach | Sow outdoors (spring) | Feb 26 – Apr 11 |
| Spinach | Sow outdoors (fall) | Aug 16 – Sep 20 |
| Radishes | Sow outdoors (spring) | Mar 5 – Apr 25 |
| Radishes | Sow outdoors (fall) | Jul 30 – Sep 30 |
| Kale | Sow outdoors (spring) | Mar 22 – Apr 11 |
| Kale | Sow outdoors (fall) | Jul 23 – Aug 30 |
| Carrots | Sow outdoors (spring) | Apr 5 – May 21 |
| Carrots | Sow outdoors (fall) | Jun 30 – Aug 15 |
| Garlic | Plant outdoors (fall) | Oct 30 – Nov 30 |
Where these dates come from
ZIP code 20830 is matched to the NOAA station Laurel 3 W, MD, 16.4 km away, at 400 ft elevation (118 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Laurel 3 W, MD (used) | 400 ft | Apr 5 | Nov 9 |
| Rockville 1 Ne, MD | 440 ft | Apr 1 | Nov 6 |
| Beltsville, MD | 145 ft | Apr 10 | Nov 1 |
| Damascus 3 Ssw, MD | 700 ft | Apr 14 | Oct 29 |
Frost dates near Olney
- Olney, MD 20832 · last Apr 5, first Nov 9
- Sandy Spring, MD 20860 · last Apr 5, first Nov 9
- Brookeville, MD 20833 · last Apr 5, first Nov 9
- Brinklow, MD 20862 · last Apr 5, first Nov 9
- Ashton, MD 20861 · last Apr 5, first Nov 9
- Silver Spring, MD 20905 · last Apr 5, first Nov 9
- Derwood, MD 20855 · last Apr 1, first Nov 6
- Rockville, MD 20853 · last Apr 5, first Nov 9
Frequently asked questions
- When is the last frost in Olney, MD?
- For ZIP code 20830, the average last spring frost (32°F) is April 5, based on NOAA 1991-2020 climate normals for the Laurel 3 W, MD weather station. There is a 1-in-10 chance of a frost after April 19.
- When is the first frost in Olney, MD?
- The average first fall frost (32°F) is November 9. There is a 1-in-10 chance of frost by October 27, so tender plants are at risk from that point on.
- How long is the growing season in 20830?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 218 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.