Average Last Frost or Freeze Dates And Map For Maryland

There is a good reason why many gardeners suggest NOT to plan tomatoes until after Mother’s Day. Early surges of warm air in spring can be deceiving. Just because the temperatures reach the 80s or even 90ºF does not mean we are safely into the growing season. In fact, often, an abnormal warm-up in March or April can be matched by an equally abnormal cool-down as the atmosphere tries to balance itself out. A late frost or freeze is still possible and can harm or kill plants, even as we head into warmer months.  So getting gardens ready can take an effort in trust and patience.

Air temperatures are measured at 5 to 6 feet above the ground. On a chilly morning, it could be 5 degrees or more colder on the ground than the air at the thermometer’s level. That can allow frost to develop on grass and cars while the air is in the upper 30s.  A freeze is when the air itself is at or below 32ºF. This is more threatening to garden plants.

Whenever I make an average map of anything weather-related in Maryland, it is colorful. There is such a wide variety of conditions thanks to the contrast between the mountains, valleys, foothills, Chesapeake Bay, all the rivers and tributaries, and the Atlantic Ocean. This does extend across to Pennsylvania and Virginia, but tightly packed contours in central Maryland reflect how difficult weather forecasting can be.

Here is a look at the ‘last’ frost and freeze dates in our region. This is when most planting can be considered safe outside. Note, this is the extreme, and the ‘safe bet’ below is a breakdown of dates the last frost or freeze that are more common for towns and cities in Maryland thanks to the University of Maryland.

Western Maryland Average Last Dates

It should be noted that on clear nights with light wind, the colder areas with the latest frost tend to be in the valleys. Hills and mountain tops get the rising warm air overnight.

North Central Maryland Average Last Dates

Also, on clear nights with light wind, the colder areas with the latest frost tend to be in the valleys. Hill tops get the rising warm air overnight.

Southern Maryland Average Last Dates

Cities tend to be warmer and earlier due to the urban heat island effect. Areas closer to the water tend to remain warmer on those last really chilly nights.

Eastern Shore/Delmarva 

Areas closer to the water tend to remain warmer on those last really chilly nights.

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RESTATING MY MESSAGE ABOUT DYSLEXIA

I am aware there are some spelling and grammar typos and occasional other glitches. I take responsibility for my mistakes and even the computer glitches I may miss. I have made a few public statements over the years, but if you are new here, you may have missed it: I have dyslexia and found out during my second year at Cornell University. It didn’t stop me from getting my meteorology degree and being the first to get the AMS CBM in the Baltimore/Washington region.

One of my professors told me that I had made it that far without knowing and to not let it be a crutch going forward. That was Mark Wysocki, and he was absolutely correct! I do miss my mistakes in my own proofreading. The autocorrect spell check on my computer sometimes does an injustice to make it worse. I also can make mistakes in forecasting. No one is perfect at predicting the future. All of the maps and information are accurate. The ‘wordy’ stuff can get sticky. 

There has been no editor who can check my work while writing and to have it ready to send out in a newsworthy timeline. Barbara Werner is a member of the web team that helps me maintain this site. She has taken it upon herself to edit typos when she is available. That could be AFTER you read this. I accept this and perhaps proves what you read is really from me… It’s part of my charm. #FITF