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Capital Weather Gang

Indicators of early spring are flourishing all around Washington

By
February 21, 2020 at 2:27 p.m. EST
Some cherry tree varieties have begun to bloom. (Jim Havard/Flickr)

From historically high temperatures to thawed soil to bursting buds, spring is starting to awaken around the Washington region — weeks ahead of time.

Despite brief cold interludes of late, it’s almost as if winter never arrived this year. With just a week until March, the winter ranks as the fifth-warmest and fifth-least snowy on record to date.

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The coldest low and high temperatures this winter, 22 and 35 degrees, will both become the warmest on record unless colder weather arrives in the coming weeks.

The lack of cold has been so persistent that ground temperature gauges have remained above freezing all winter, the warmest on record.

The indicators of a lackluster winter and budding spring are many.

In the snow dumps

Washington’s historical snowfall peak in late January and early February has come and gone with nothing to show for it. An entire year has elapsed since Washington’s last inch of snow, and just 0.6 inches accumulated this winter.

In “normal” winters, about 13 of the usual 15.4 inches have fallen by this time. This would imply we still would have 2.5 inches to go, which would probably feel like a blizzard this winter.

Cold in short supply

If you can’t remember where your scarf is, there’s good reason.

Every day that passes makes it more likely that Washington’s 22-degree low this winter will be the coldest. If that’s the case, it will become the warmest winter low on record, well above the previous mark of 19 degrees from the winters of 1952-1953 and 2001-2002.

For perspective, over the past 30 winters, the average lowest temperature was 11.6 degrees.

In the coming weeks, if we do not experience a high temperature below 35 degrees, that will beat the old warmest mark (for the lowest winter high temperature) of 34 degrees from the winter of 1997-1998. Over the past 30 winters, the average lowest high temperature has been 24 degrees.

The absence of a day with a freezing temperature from start to finish fits into the long-term trend toward fewer such days each winter. The most recent 30-year average is about seven days per winter, down from 14 in 1940.

On the flip side, the two days in which high temperatures reached at least 70 degrees this winter follows an upward trend. In earlier decades, it was not unusual to see several years in a row with no 70-degree days, but we have seen them in every winter since 2010-2011.

Warm air and warm ground

With cold air consistently lacking, it has not been cold enough for long enough to freeze the ground. While this region does not tend to see superlengthy spells of subfreezing weather, this year’s warm ground is nonetheless a rarity.

The closest monitoring site with ground temperature data, in Powder Mill, Md., just northeast of the Beltway, has seen a minimum reading of 36 degrees two inches below the surface. This is the first year in its 20-year record with such a mild reading. Other ground-temperature monitoring sites in the Mid-Atlantic region show similarly mild readings.

Trees, plants and flowers waking up

The USA National Phenology Network, which tracks the timing of seasonal events in plants and animals, shows spring rapidly advancing into the Mid-Atlantic based on emerging vegetation.

Green leaves are displaying just south of Washington. Even into the city, there are increasing numbers of plants now showing leaves while buds flower. The Phenology Network estimated that spring is arriving up to 24 days early in parts of the Washington region.

Spring has arrived weeks early in the South. Flowers are blooming, and that could be a problem.

Due to the recent cold blasts, the rate of greening has slowed over the past week. Even so, at least three days this month have featured high tree pollen levels — including as recently as Tuesday. With more warmth around the corner, that number is likely to grow. While some tree pollen is common in February, levels like we’ve seen this year are unusual.

When it comes to the famed cherry blossoms, March temperatures are the leading predictor of how early or late they will bloom, so it’s still a bit early to make predictions.

The National Park Service has not begun its reports on the cherry blossoms’ bud phase, although they appeared to have reached the initial green bud stage based on a recent visit to the Tidal Basin. Historically, peak bloom averages four weeks after this stage, but has ranged between 17 and 40 days in recent years.

Jason Samenow contributed to this report.

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