Maryland weather and outdoor projects
Maryland’s weather varies from the mountains in the west to Chesapeake Bay and the Atlantic coast in the east. The Baltimore and Washington suburbs have hot, humid summers and cool winters with occasional snow. Western Maryland is colder and snowier.
Spring and fall give the best painting and staining weather, with milder temperatures and lower humidity than July and August. Summer storms and humid nights can bring dew on fresh finishes. Freeze-thaw cycles through winter are hard on concrete steps and driveways, so cure and seal new concrete well before cold weather.
Frost dates in Maryland
In Baltimore (BWI), the median last spring freeze (32°F) is around April 10 and the median first fall freeze is around October 31, a frost-free season of about 204 days.
How Maryland compares with other states
Baltimore (BWI) is tied for the 14th-shortest deck staining season of the 50 state main stations (4 good months). Baltimore (BWI) is tied for the 20th-most rainy days of the 50 state main stations (75 a year with 0.1 in or more). Baltimore (BWI) is tied for the 20th-most humid summer afternoons of the 47 state main stations (50% humidity at 3 PM, June–August).
| Measure (Baltimore (BWI)) | Value | Rank, highest first |
|---|---|---|
| Deck staining season | 4 good months | 20th of 50 |
| Frost-free season | 204 days | 27th of 50 |
| Freezing nights | 93 a year | 24th of 50 |
| Rainy days | 75 a year with 0.1 in or more | 20th of 50 |
| Days at 90°F or hotter | 34 a year | 22nd of 50 |
| Summer afternoons | 50% humidity at 3 PM, June–August | 20th of 47 |
Best time to stain a deck in Maryland
In Baltimore (BWI), the most reliable months are May–June and August–September. April, July and October can also work on the right days (average highs Apr 67°F, Jul 89°F, Oct 68°F). December–March is too cold, with average highs around 48°F. In November, nights average about 37°F, too cold for the coating to dry and cure overnight. In April and October, nights average about 45°F, so finish early on mild days and check the overnight low. July is hot, with highs near 89°F, so start early and keep out of full afternoon sun.
Best time to paint outside in Maryland
In Baltimore (BWI), the most reliable months are May–June and August–October. March–April, July and November can also work on the right days. December–February is too cold, with average highs around 46°F. March and November are cool, with highs around 56°F, so choose the warmest afternoons. In April, nights average about 44°F, so finish early on mild days and check the overnight low. July is hot, with highs near 89°F, so start early and keep out of full afternoon sun.
Best time to pour concrete in Maryland
In Baltimore (BWI), the most reliable months are May–October. April can also work on the right days (average highs Apr 67°F). November–March averages about 18 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. April brings about 2 freezing nights a month, so pick a mild spell and keep curing blankets on hand.
Best time to seal a driveway in Maryland
In Baltimore (BWI), the most reliable months are May–September. April and October can also work on the right days (average highs Apr 67°F, Oct 68°F). November–March is too cold, with average highs around 50°F. April is cool, with highs around 67°F, so choose the warmest afternoons. In October, nights average about 47°F, so finish early on mild days and check the overnight low.
Best time to fertilize or treat a lawn in Maryland
In Baltimore (BWI), the most reliable months are April–June and September–October. March, July–August and November can also work on the right days. December–February is too cold, with average highs around 46°F. March and November are cool, with highs around 56°F, so choose the warmest afternoons. July–August is hot, with highs near 88°F, so start early and keep out of full afternoon sun.
Monthly weather in Baltimore (BWI)
| Month | Avg high | Avg low | Wet days* | Rain | 3 PM humidity | Freezing nights |
|---|---|---|---|---|---|---|
| January | 43°F | 25°F | 6 | 3.1 in | 50% | 24 |
| February | 46°F | 27°F | 6 | 2.9 in | 46% | 21 |
| March | 55°F | 34°F | 7 | 4.0 in | 43% | 14 |
| April | 67°F | 44°F | 6 | 3.4 in | 43% | 2 |
| May | 76°F | 53°F | 7 | 3.9 in | 48% | 0 |
| June | 84°F | 63°F | 7 | 4.0 in | 50% | 0 |
| July | 89°F | 68°F | 7 | 4.5 in | 49% | 0 |
| August | 87°F | 66°F | 6 | 4.1 in | 51% | 0 |
| September | 80°F | 59°F | 6 | 4.4 in | 51% | 0 |
| October | 68°F | 47°F | 5 | 3.9 in | 51% | 1 |
| November | 57°F | 37°F | 5 | 3.1 in | 48% | 10 |
| December | 48°F | 30°F | 6 | 3.7 in | 52% | 21 |
*Days with 0.1 inch of rain or more; column notes.
Source: NOAA NCEI U.S. Climate Normals 1991–2020 for BALTIMORE WASH INTL AP. See how the ratings work and how late in fall you can stain, paint or seal.
Frequently asked questions
When is the best time to stain a deck in Maryland?
In Baltimore (BWI), May–June and August–September.
When is the last frost in Maryland?
Baltimore (BWI): around April 10.
Can you pour concrete in winter in Maryland?
Yes, with cold-weather practices: Baltimore (BWI) averages about 66 freezing nights from December to February, so fresh concrete needs insulated blankets, a heated enclosure or an accelerated mix, and must not freeze in the first 48 hours. Many homeowners wait for spring.
What months are best for sealing a driveway in Maryland?
In Baltimore (BWI), May–September.