A blossom close-up with the Washington Monument in the background in late March 2009. (Kevin Ambrose)

National Park Service peak bloom date forecast: March 24-28

*Capital Weather Gang peak bloom date forecast: March 18-22

Earliest peak on record: March 17, 2000

Before this super warm weather pattern became apparent, Rob DeFeo, chief horticulturalist at the National Park Service, had predicted a bloom date of March 24-31. But he’s narrowed that window to the early side of the range, and now forecasts a peak bloom from March 24-28.

DeFeo has made blossom predictions for 20 years and has been right 16 or 17 times he said. But he suggested this could be one of those rare years that he’s wrong.

“Every time I’ve missed, it’s because of weather conditions we have right now,” he said.

With a string of sunny days above 70 ahead along with mild nights, the blossoms should pass a point of no return.

“Once they come on, they’re really hard to stop,” DeFeo said.

The lack of cold at night, in particular, should allow the blossoms to fluorish.

“When you get night time temperatures above 45-50, they don’t slow down like they normally do,” he said. “Cold nights shut them down.”

Over the next week, night time low temperatures are forecast to be in the upper 40s to mid-50s - some 15-20 degrees above normal.

“My nightmare now is this weather,” Japanese ambassador to the U.S. Ichiro Fujisaki said at press briefing today at the National Press Building.

“What are we going to do if all the cherry blossoms bloom before we start [the annual National Cherry Blossom Festival]?,” he said. “That’s my nightmare.”

*Rationale for Capital Weather Gang forecast

According to DeFeo, temperatures in March are the most important predictor for the bloom date. I compared temperatures from the record early bloom year of March 2000 to the current March - and they’re very similar. Although first 10 days of March this year (while well above normal) were substantially cooler than March 2000, the upcoming week will be significantly warmer than 2000 (especially at night), leveling the playing field.

The average temperature (between the high and low) from February 23 to March 17 in 2000 and 2012. The dashed line in 2012 indicates the forecast average temperature.

It’s hard to say whether the blossoms can catch up and reach peak bloom as early as 2000. But given the weather forecast, it’s unlikely they’ll lose ground. Hence, I expect peak bloom no later than about three or four days after the record set in 2000. Peak bloom should occur between March 18-22.

Bloom periods start a few days before the peak bloom date and can last up to 10 days after, although there is some year-to-year variability. In other words, it’s possible some blossoms may be out in time for St. Patrick’s day...

(Caveat: there is, of course, uncertainty in this prediction. And, in the spirit of transparency, this is my first year trying this. We will make this an annual CWG tradition and I will try to learn along the way.)


Washington’s century-old cherry trees: wizened but still able to bust a bloom

Your Cherry Blossom photos (gallery)
Poll: when will the cherry blossoms peak?
Cherry blossoms with an overcast sky (PHOTOS, 2011)
Washington’s cherry blossoms in the snow (PHOTOS, 2011)
A cherry blossom bird’s-eye view (PHOTOS, 2010)
Cherry Blossoms Wind Down as D.C. Greens Up (PHOTOS, 2009)
Cherry Blossom Morning (PHOTOS 2009)
Washington D.C.’s Cherry Blossom Bloom Begins (PHOTOS, 2009)
Photography: Falling Blossoms & Spring Scenes, Kevin Ambrose (2008)
Photography: A Blooming Good Time (2008)
Photography: Glorious Cherry Blossom Sunrise (2008)
Photography: Cherry Blossoms by Night (2008)
Photography: Flying High as Spring Blossoms (2008)