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Cherry blossom forecast: Peak bloom will be close to record-early this year

The blossoms at the Tidal Basin at peak bloom on March 25, 2016. (Kevin Ambrose)

(This story, originally posted Tuesday Feb. 28, was updated on Wednesday, March 1 to incorporate the National Park Service peak bloom forecast.)

After off-the-charts warmth in February, trees and flowers in the District have responded by initiating their bloom cycles two to three weeks earlier than normal.

Between the record-warm February and the outlook for more above-average temperatures in the coming weeks, we predict the cherry trees will reach peak bloom between March 15 and 19 — about two weeks ahead of the April 1 average peak bloom. If it happens on March 15, it will tie for the earliest on record from 1990. The National Park Service has documented peak bloom dates since 1921.

For its park, the National Park Service announced Wednesday that it predicts peak bloom to occur between March 14 and 17, consistent with our forecast.

Cherry blossom peak bloom this year could be the earliest on record

Peak bloom, defined as when 70 percent of the cherry blossoms along the Tidal Basin are in bloom, could well occur before this year’s National Cherry Blossom Festival, which runs between March 20 and April 16.

Blossoms start to appear on trees several days before the peak bloom date and, weather permitting, can remain for a week or so. However, in some years, petals fall off sooner because of wind, rain or frost.

This year is likely to be the second in a row with a substantially earlier-than-normal bloom. In 2016, peak bloom occurred March 25. But in the three-year stretch from 2013 to 2015, peak bloom was later than normal, occurring April 9 or 10. The latest peak bloom on record occurred April 18, 1958.

Since records began in 1921, the average peak bloom date has advanced about five days earlier in the year as March temperatures have warmed.

Our forecast rationale

The bloom process for the cherry blossoms has already begun, and it’s well ahead of normal. Green buds emerged on the cherry tree we check on Feb. 24. We inspected the buds Feb. 26, and some were starting to show florets or swollen buds, the next stage in blossom development and beginning of the flowering stage.

The warm weather forecast in Washington on Tuesday and, particularly, Wednesday — when it may hit 80 — may push buds to their next stage late this week — the extension of florets.

Cherry blossom bloom phases from National Park Service

Typically, it’s about 12 to 17 days to peak bloom once florets extend, but in recent years it has happened as fast as six days. The bloom cycle progresses most quickly when temperatures spike into the 70s and 80s.

Because temperatures are forecast to turn sharply colder Friday and Saturday, we expect the bloom process will slow significantly. But milder air early next week should allow it to pick back up.

There is the possibility of a second burst of chilly air around March 8 to 10, when the bloom process could again slow. But we think mild air moving in after March 10 should be sufficient to push the blossom process toward the finish line between March 15 and 19.

Our confidence in this outlook is only moderate, simply because we’re in somewhat uncharted territory with the bloom process so advanced so soon. Ordinarily, the best predictor for the cherry blossom peak bloom date is the March average temperature. But because the buds are so far along this year, March’s overall temperature is less important, and more important is the buds’ present condition and the temperature forecast for the next two weeks.

Risks to the forecast

If temperatures end up being milder-than-predicted in the next two weeks, the earliest peak bloom on record would probably occur. Especially if we have sunny days into the 60s and 70s (or higher), that will really move the bloom process along.

But if temperatures are a little colder-than-predicted, the bloom cycle may take its time. Cloudy days in the 40s (or lower) and cold nights (in the 30s and colder) could delay the peak bloom until after March 20.

Below find our likelihood of different outcomes …

Peak bloom March 15-19: 50 percent chance (most likely)
Peak bloom March 20-24: 20 percent
Peak bloom March 10-14: 20 percent
Outside the March 10-24 window: 10 percent

How have our forecasts done historically?

This is the sixth year we’ve issued a cherry blossom peak bloom forecast. We’ve had reasonably good forecasts the previous five years — hitting the peak bloom within our forecast window four times.

In 2016, we predicted a peak bloom date of March 26 (March 24-28 window), and it occurred March 25.

In 2015, we predicted a peak bloom date of April 11 (April 9-13 window), and it occurred April 10.

In 2014, we predicted a peak bloom date of April 9 (April 7-11 window), and it occurred April 10.

In 2013, we predicted an April 5 peak bloom date (April 3-7 period), and it occurred April 9.

In the very warm 2012, we predicted a peak bloom date of March 20, the same day it actually occurred.

[Capital Weather Gang Cherry Blossom coverage]

Blossom photos by Kevin Ambrose

To track the blossom bloom, every week we’ll post a photo of the cherry tree (below) at the Tidal Basin as we transition from winter to spring. This is the second week of such posts. Here’s the post from week one.

We’ll return to the Tidal Basin next weekend to photograph the trees for another status report.

More cherry blossom coverage

Tracking the cherry blossoms to full bloom — Week one

The warmer winter means cherry blossoms will peak early

Tracking blossoms to full bloom — what a difference a year makes

All Capital Weather Gang cherry blossom posts