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Cherry blossoms: Here's how peak bloom is predicted

“All of that goes into the mix so that hopefully on March first we come up with a four day window for when peak bloom is going to occur.”

WASHINGTON — One week from today, we’ll learn from the National Park Service when they expect the beloved cherry blossoms around the tidal basin to hit peak bloom. That’s when 70 percent of the trees are fully blossoming.

So how exactly do they make that call?


How is “peak bloom” for the Tidal Basin cherry blossoms predicted?


  • Michael Litterst, spokesman for National Park Service 
  • The National Cherry Blossom Festival


Watching grass grow is an activity for the bored, but predicting blossoms’ bloom may be best for the brave.

“No small amount of pressure,” says Mike Litterst of the National Park Service of the sentiment each year leading up to their peak bloom prediction–which typically drops in late February to early March.

“It puts us close enough that we can make an educated prediction,” he explained. “So much of this is contingent upon what's the high temperature going to be leading up to peak bloom. Really, that's only reliable about ten days out.”

He explains the countdown begins once the trees around the Tidal Basin reach dormancy over the winter. From there, NPS counts “degree days,” when the high temp each day contributes to a grand total of 217.

“When you reach 217-degree days, that's when peak bloom is going to occur. A day in the seventies is going to give you more points towards that than a day in the fifties or the forties,” said Litterst.

They also watch the “indicator tree,” which pretty reliably blooms about two weeks ahead of the others–plus historic patterns, even what other trees are starting to flower.

“All of that goes into the mix so that hopefully on March first we come up with a four-day window for when peak bloom is going to occur.”

There’s nothing magic about that March 1 date–Litterst says it’s just the soonest making a prediction makes sense.

“Cherry Blossom Festival is sort of unique in that it's planned not by the calendar but by the thermometer, so that does present challenges,” said Litterst. This year the National Cherry Blossom Festival is from March 20 through April 16–casting a pretty wide net to catch peak bloom, whenever it’s ultimately forecast. “We know the reservations are going to start to be made shortly after that, and we hope that we're not going to have to adjust that at all afterward.” 

Any opportunity to get a scoop one week early?

“You can ask, but I don't have any insider information. The trees are the ones that have the information and they're not talking.”

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