Fall in zone 7bPhoto: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons
Frost dates for ZIP 20646 (La Plata, MD)
Average last spring and first fall frost dates with 10%, 50% and 90% odds, from NOAA's 1991–2020 climate normals for the nearest weather station, Mechanicsville 5 NE, MD (15 miles away).
- Average last spring frostApr 1750% chance of a 32°F freeze after this date
- Average first fall frostOct 2750% chance of a 32°F freeze by this date
- Growing season (frost-free)195 daysmedian, 32°F threshold
- USDA hardiness zone7b5 to 10°F avg. coldest night
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This week in your yard
As of Oct 18, 2026, from your frost dates, zone and soil temperature. Lawn timing · Vegetables · Pruning · Plants
Soil temperature now
2-inch depth
63°F 55°F or warmer
24-hour average · latest 60°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Powder Mill (36 mi).
4-inch depth
63°F 55°F or warmer
24-hour average · latest 58°F, as of Oct 18, 2:00 AM CDT
Estimate Not a measurement at this ZIP: distance-weighted average of Powder Mill (36 mi).
Fall: Texas A&M AgriLife times fall pre-emergent (for winter weeds such as annual bluegrass) to soil cooling to about 70°F for several days. The 50–55°F band is the spring trigger. Always read and follow the product label.
7-day forecast and frost risk
The latest National Weather Service 7-day forecast and any Frost Advisory or Freeze Warning for 20646 load here. You can also open the NWS forecast for this ZIP.
Pre-emergent
Soil is 63°F at 4 inches (estimated soil temperature, not a station reading). Fall pre-emergent (annual bluegrass, winter weeds): window open as soil cools through the 70s and 60s.
Fertilizer window
Lawn region: Transition zone. Timing only; always follow the product label.
- Bermudagrass (warm-season): Spring: Several weeks after the lawn is fully green (April–May) (about Jun 2 here, using green-up about 3–4 weeks after your average last frost); Summer: Every 4–6 weeks through mid-August (heaviest feeder of the group); Late: Light, low-nitrogen/high-potassium feeding about 4 weeks before first frost, or skip. Avoid: Heavy late-fall nitrogen (linked to spring dead spot).
- Tall fescue (cool-season): Early fall: September (main feeding); Late fall: November, while still green; Late winter: Optional light feeding February–March. Avoid: Feeding after mid-spring and through summer in the transition zone (stress and brown patch).
Plant now
No vegetable planting windows are open this week.
Prune now
No frost-timed pruning windows are open this week.
Your average first frost is Oct 27: skip heavy pruning in the 6–8 weeks before it, because new growth may not harden off in time.
Spring-flowering shrubs are pruned right after their flowers fade, not by date. See the pruning guide.
Last spring frost odds
| Chance of a 32°F freeze after this date | Date |
|---|---|
| 90% (early: most years still freeze after this) | Mar 31 |
| 50% (the "average" last frost) | Apr 17 |
| 10% (cautious: only 1 year in 10 freezes later) | May 2 |
Most gardeners plant frost-tender crops (tomatoes, peppers, basil) after the 50% date, and closer to the 10% date for less risk.
First fall frost odds
| Chance the first 32°F freeze has happened by this date | Date |
|---|---|
| 10% (early: 1 year in 10 freezes this soon) | Oct 12 |
| 50% (the "average" first frost) | Oct 27 |
| 90% (late: most years have frozen by now) | Nov 9 |
Light frost, freeze and hard freeze
| Threshold | Last spring (50%) | First fall (50%) |
|---|---|---|
| 36°F (light frost possible on clear, calm nights) | Apr 30 | Oct 16 |
| 32°F (freeze) | Apr 17 | Oct 27 |
| 28°F (hard freeze) | Apr 2 | Nov 6 |
n/a means NOAA did not publish a date at that threshold for this station (usually because it rarely gets that cold).
Vegetable planting calendar for 20646
Dates count from your average last spring frost (Apr 17) and first fall frost (Oct 27). Half of years have a frost after the spring date, so give tender crops (tomatoes, peppers, squash) some slack.
| Crop | Start indoors | Spring planting | Fall planting |
|---|---|---|---|
| Tomato | Feb 20–Mar 6 | Apr 24–May 8 (transplant) | – |
| Pepper (sweet and hot) | Feb 6–20 | May 1–15 (transplant) | – |
| Eggplant | Feb 6–20 | May 1–15 (transplant) | – |
| Tomatillo | Feb 20–Mar 6 | Apr 24–May 8 (transplant) | – |
| Lettuce | Feb 20–Mar 6 | Mar 27–Apr 17 (transplant) Mar 20–May 1 (sow outdoors) | Sep 1–22 (transplant) Aug 18–Sep 15 (sowing) |
| Spinach | – | Mar 6–27 (sow outdoors) | Sep 1–22 (sowing) |
| Kale | Feb 20–Mar 6 | Mar 20–Apr 3 (transplant) Mar 20–Apr 3 (sow outdoors) | Aug 4–Sep 1 (transplant) Jul 21–Aug 18 (sowing) |
| Collards | Feb 20–Mar 6 | Mar 20–Apr 17 (transplant) Mar 20–Apr 17 (sow outdoors) | Aug 4–Sep 1 (transplant) Jul 21–Aug 18 (sowing) |
| Broccoli | Feb 6–20 | Mar 20–Apr 3 (transplant) | Jul 21–Aug 18 (transplant) |
| Cabbage | Feb 6–20 | Mar 20–Apr 3 (transplant) | Jul 21–Aug 18 (transplant) |
| Cauliflower | Feb 6–20 | Apr 3–17 (transplant) | Jul 21–Aug 18 (transplant) |
| Brussels sprouts | Jan 23–Feb 6 | Mar 20–Apr 3 (transplant) | Jul 7–28 (transplant) |
| Kohlrabi | Feb 20–Mar 6 | Mar 20–Apr 3 (transplant) Mar 20–Apr 3 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Bok choy / Asian greens | – | Mar 20–Apr 3 (sow outdoors) | Sep 1–15 (sowing) |
| Arugula | – | Mar 20–Apr 17 (sow outdoors) | Sep 1–29 (sowing) |
| Mustard greens | – | Mar 20–Apr 10 (sow outdoors) | Sep 1–15 (sowing) |
| Swiss chard | Mar 6–20 | Apr 3–24 (transplant) Apr 3–May 1 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Beet | – | Mar 20–Apr 17 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Carrot | – | Mar 27–Apr 24 (sow outdoors) | Aug 4–18 (sowing) |
| Radish | – | Mar 13–Apr 24 (sow outdoors) | Sep 15–29 (sowing) |
| Turnip | – | Mar 20–Apr 10 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Parsnip | – | Mar 27–Apr 17 (sow outdoors) | – |
| Pea (garden, snap, snow) | – | Feb 20–Mar 20 (sow outdoors) | Aug 4–18 (sowing) |
| Onion (bulbing) | Jan 23–Feb 6 | Mar 6–20 (transplant) | – |
| Green onion / scallion | – | Mar 6–Apr 3 (sow outdoors) | Aug 18–Sep 1 (sowing) |
| Leek | Jan 23–Feb 6 | Mar 20–Apr 3 (transplant) | – |
| Garlic | – | – | Sep 15–Oct 13 (sowing) |
| Shallot | – | Mar 6–20 (transplant) | Sep 15–Oct 13 (sowing) |
| Potato | – | Mar 20–Apr 3 (transplant) | Jul 7–21 (transplant) |
| Sweet potato | – | May 8–22 (transplant) | – |
| Sweet corn | – | Apr 24–May 8 (sow outdoors) | – |
| Bean, bush (snap) | – | Apr 24–May 8 (sow outdoors) | – |
| Bean, pole | – | Apr 24–May 8 (sow outdoors) | – |
| Lima bean | – | May 1–15 (sow outdoors) | – |
| Southern pea (cowpea, black-eyed pea) | – | May 8–29 (sow outdoors) | – |
| Cucumber | Mar 20–27 | Apr 24–May 8 (transplant) Apr 24–May 8 (sow outdoors) | – |
| Summer squash / zucchini | Mar 20–27 | Apr 24–May 8 (transplant) Apr 24–May 8 (sow outdoors) | – |
| Winter squash | Mar 20–27 | Apr 24–May 8 (transplant) Apr 24–May 8 (sow outdoors) | – |
| Pumpkin | – | Apr 24–May 8 (sow outdoors) | – |
| Watermelon | Mar 20–27 | May 1–15 (transplant) May 1–15 (sow outdoors) | – |
| Cantaloupe / muskmelon | Mar 20–27 | May 1–15 (transplant) May 1–15 (sow outdoors) | – |
| Okra | Mar 6–20 | May 1–15 (transplant) May 1–15 (sow outdoors) | – |
| Celery | Jan 23–Feb 6 | Apr 24–May 1 (transplant) | – |
| Basil | Mar 6–20 | Apr 24–May 8 (transplant) Apr 24–May 8 (sow outdoors) | – |
| Cilantro | – | Apr 3–May 1 (sow outdoors) | Sep 1–15 (sowing) |
| Parsley | Feb 6–20 | Apr 3–17 (transplant) Mar 27–Apr 17 (sow outdoors) | – |
| Dill | – | Apr 17–May 1 (sow outdoors) | Sep 1–15 (sowing) |
| Sunflower | – | Apr 17–May 1 (sow outdoors) | – |
| Asparagus (crowns) | – | Mar 20–Apr 3 (transplant) | – |
| Rhubarb (crowns) | – | Mar 20–Apr 3 (transplant) | – |
| Strawberry (plants) | – | Mar 20–Apr 3 (transplant) | Aug 18–Sep 15 (transplant) |
Typical ranges from university extension planting calendars, adjusted to your frost dates. Probabilities, not guarantees. Fall windows that would overlap spring planting are left out, as are fall crops of frost-tender plants where the frost-free season is under 210 days.
Where these numbers come from
Station: Mechanicsville 5 NE, MD (NOAA GHCN-Daily ID USC00185865), elevation 100 ft, 15.0 miles from the ZIP's center point. NOAA completeness flag: S (standard, 24+ years).
Nearby stations
| Station | Distance | Last frost (50%) | First frost (50%) |
|---|---|---|---|
| Quantico Mcas, VA | 16 mi | Mar 28 | Nov 8 |
| Oxon Hill, MD | 19 mi | Apr 3 | Nov 8 |
| Washington Reagan AP, VA | 23 mi | Mar 24 | Nov 18 |
The average last-frost dates of these stations span 24 days, a rough guide to local variation. See data sources & methods.
Frost questions for 20646
When is the last frost in 20646?
The average (50% chance) last spring freeze of 32°F for ZIP 20646 is April 17. For a more cautious planting date, use May 2, when only 1 year in 10 still sees a later freeze.
When is the first frost in 20646?
The average first fall freeze is October 27. In 1 year in 10 it comes by October 12.
What hardiness zone is 20646?
ZIP 20646 is in USDA zone 7b (5 to 10°F average coldest winter night), per the 2023 USDA Plant Hardiness Zone Map ZIP listing.
What is the soil temperature in 20646 right now?
This page shows the latest 2-inch and 4-inch soil temperature from the nearest public soil station (USDA SCAN, NOAA USCRN or TexMesonet), or a labeled estimate when no station is close, against the 50–55°F spring pre-emergent band.
Nearby ZIP codes
20677 Port Tobacco Village 20675 Pomfret 20611 20695 Waldorf 20693 20602 Waldorf 20632 20603 Bensville
Other ZIP codes in Charles County
20601 20602 20603 20611 20612 20616 20617 20622 20625 20632 20637 20640 20645 20658 20661 20662 20664 20675 20677 20693 20695 All Charles County frost dates · Maryland frost dates
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- Freeze alerts
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Free. One weekly email plus alerts when your ZIP has a frost or a soil-temperature change worth acting on. After you submit, Kit (our email provider) sends a confirmation email: check your email and click the link to confirm. You aren't subscribed until you do. We collect only your email address and ZIP, sent to Kit to deliver The Dial. Unsubscribe anytime.