Frost Dates: First and last frost dates for Rockville, MD
ℹ️ How to read these charts for the spring
As spring unfolds, the risk of frost gradually decreases each day until your tender plants are finally safe. The probabilities shown in the chart help you make smart decisions about when to plant.
While frost typically forms at 32°F, tender plants can be damaged even when temperatures are slightly higher. Air temperatures are often measured several feet above the ground, but temperatures at plant level can be several degrees colder. Protected areas like porches help by blocking radiational cooling. Given these variables, we consider 36°F the "caution zone" for frost-sensitive plants.
Key dates for your spring planting:
- By May 21, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
- Around April 29, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
- Before April 15, there's still an 80% risk of frost — too early for tomatoes and other tender plants unless you're prepared to protect them
If the 10-day forecast shows no temperatures below 40°F, you might safely plant earlier than the above dates suggest. Many gardeners watch for this weather window to get a head start on the growing season.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Last 16° | Mar 25 | Mar 15 | Mar 7 | Mar 1 | Feb 23 | Feb 18 | Feb 11 | Feb 4 | Jan 25 |
| Last 20° | Mar 31 | Mar 25 | Mar 20 | Mar 16 | Mar 12 | Mar 8 | Mar 4 | Feb 27 | Feb 21 |
| Last 24° | Apr 11 | Apr 5 | Mar 31 | Mar 27 | Mar 24 | Mar 20 | Mar 16 | Mar 12 | Mar 6 |
| Last 28° | Apr 23 | Apr 16 | Apr 12 | Apr 8 | Apr 4 | Mar 31 | Mar 27 | Mar 23 | Mar 17 |
| Last 32° | May 7 | Apr 30 | Apr 25 | Apr 20 | Apr 16 | Apr 12 | Apr 8 | Apr 2 | Mar 26 |
| Last 36° | May 21 | May 13 | May 8 | May 3 | Apr 29 | Apr 25 | Apr 20 | Apr 15 | Apr 7 |
ℹ️ How to read these charts for the fall
As summer ends in Rockville, MD, nighttime temperatures begin to drop, and your risk of frost increases with each passing day. Knowing when to expect frost helps you harvest sensitive crops and extend your growing season with protection methods.
The chart below shows the probability of experiencing specific temperatures on various dates. Here's what this means for your garden:
These probabilities help you time your end-of-season harvests and know when to apply protective measures like row covers, cloches, or cold frames to extend your harvest.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| First 16° | Nov 24 | Dec 2 | Dec 7 | Dec 12 | Dec 16 | Dec 20 | Dec 25 | Dec 30 | Jan 6 |
| First 20° | Nov 6 | Nov 15 | Nov 21 | Nov 26 | Dec 1 | Dec 6 | Dec 12 | Dec 18 | Dec 27 |
| First 24° | Oct 21 | Oct 30 | Nov 6 | Nov 12 | Nov 17 | Nov 23 | Nov 28 | Dec 5 | Dec 15 |
| First 28° | Oct 12 | Oct 19 | Oct 24 | Oct 28 | Nov 1 | Nov 5 | Nov 9 | Nov 14 | Nov 21 |
| First 32° | Oct 3 | Oct 9 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 29 | Nov 3 | Nov 9 |
| First 36° | Sep 23 | Sep 29 | Oct 3 | Oct 7 | Oct 10 | Oct 14 | Oct 17 | Oct 22 | Oct 28 |
📍 Frost Dates for other nearby locations
- Dalecarlia Rsvr, MD 11.5 mi
- Vienna, VA 14.9 mi
- Beltsville, MD 17.2 mi
- Natl Arboretum Dc, MD 18.7 mi
- Laurel, MD 18.8 mi
- Washington Reagan, VA 19.5 mi
- Clarksville, MD 20.2 mi
- Washgtn Dulles, VA 22.8 mi
- Glenn Dale Bell Stn, MD 26.9 mi
- Frederick Police Brks, MD 29.0 mi
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Data is provided by the NOAA National Centers for Environmental Information.