Hard Freeze, But No Frost: What Gives?

– Posted in: FAQ, Weather
6 comments

Frostless lawn

When I got up this morning, it was 19F, but I saw a sight similar to this one. No frost on the ground at all.

Very early this morning, the temperature bottomed out at 18F, so my max-min thermometer tells me. And yet, when I looked out my window, there was not a speck of frost on the grass. If I hadn’t consulted the thermometer, I would have thought it was a lovely spring day out there. (The grass has grown up and is even greener than depicted in the photo above, which was taken about two weeks ago.)

How can that be? Some of you may already know the answer, but I asked the National Weather Service office in Binghamton, NY just to be sure, and they confirmed my suspicions. The air was very dry and the dew point was even lower than last night’s low. To refresh your memory, the dew point is the temperature at which the moisture in the air condenses onto surfaces such as the grass. If the dew point is lower than the air temperature, then even if the air temperature is below freezing, you won’t see any frost.

Dry air and low dew points are typical for winter, but most of the time the ground is snow-covered (at least around here) and we don’t notice the lack of frost. This was just one of those times when it was cold and dry but not snow covered–and the lawn was lushly green, making the absence of frost even more noticeable.

Further Reading

The Dew What? What Is The Dew Point?
A Gardener’s Guide to Frost: Outwit the Weather and Extend the Spring and Fall Seasons

About the Author

Kathy Purdy is a colchicum evangelist, converting unsuspecting gardeners into colchicophiles. She would be delighted to speak to your group about colchicums or other gardening topics. Kathy’s been writing since 4th grade, gardening since high school, and blogging since 2002.

In the end, this may be the most important thing about frost: Frost slows us down. In spring, it tempers our eagerness. In fall, it brings closure and rest. In our gotta-go world–where every nanosecond seems to count–slowness can be a great gift. So rather than see Jack Frost as an adversary, you could choose to greet him as a friend.

~Philip Harnden in A Gardener’s Guide to Frost: Outwit the Weather and Extend the Spring and Fall Seasons

6 Comments… add one

Heatblizzard November 25, 2013, 9:46 am

What was the humidity at the time of that picture? You can look it up at Weather Underground airport for that day and tell me as I do NOT know the date of you’re picture.

Deborah Banks March 28, 2012, 10:04 am

I wondered about it too. It was 14 degrees here yesterday morning, and the grass was green and fresh looking.

Victoria March 28, 2012, 9:49 am

Thank you for this info. l wondered about it as well. l did bring in my hummingbird feeders, l have seen them a month earlier then usual!

Flâneur Gardener March 28, 2012, 12:24 am

Most of the winter here in Denmark is snow-free, so I guess I’m used freezing with no frost; here it seems that we mainly get that sort of sparkling frost in autumn and spring, and then in winter we get the frost-free freezes.

Kathy Purdy March 28, 2012, 11:52 am

In the winter, if we don’t have snow, the grass is brown and the earth is frozen solid. Under those circumstances, we aren’t expecting to see frost either. Because of the unseasonably warm weather, it looks a good month later outside than it really is. I think that’s what made the absence of frost so striking.

Gail March 27, 2012, 11:02 pm

Fascinating…I’m not sure I’ve seen, perhaps, not noticed that here. gail

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