Washington’s recent weather, while not especially stormy or frigid, has tended to be cooler than average and more characteristic of winter than spring. But a pulse of warmth is in the forecast next week, and before long buds will be bursting, pollen exploding and our landscape will transform from barren brown to lush green.

All the while, Washington’s famous cherry blossoms will start their progression from green buds to magnificent pink and white flowery blooms.

Based on an evaluation of past, present and predicted weather conditions, we are forecasting peak bloom for the cherry blossoms this year to occur around April 1, or within the window between March 30 and April 3. This falls right in the middle of historical averages.

Over the last 30 years, peak bloom has averaged around March 31. If we look at the longer 100-year average, the average peak bloom date is a bit later, on April 3. The date has trended several days earlier in recent decades due to our warming climate.

March 15, 1990 marks the earliest peak bloom on record while April 18, 1958 is the latest peak. Last year, peak bloom occurred on March 20, tied for the third-earliest on record.

Peak bloom is reached when 70 percent of the cherry blossoms flower along the Tidal Basin. If our forecast holds, peak bloom will coincide with the National Cherry Blossom Festival, set for March 20 to April 11.

Our peak bloom forecast is similar to that of the National Park Service, which is calling for a peak bloom between April 2 and 5.

But if you’re planning to see the blossoms in person when they’re at their prime, you may want to manage your expectations.

Due to the coronavirus pandemic, the National Park Service is discouraging the public from visiting the Tidal Basin this year and is recommending viewing the blossoms online instead. Early this week, Jeff Reinbold of the Park Service said the agency has not decided whether to offer some limited in-person viewing opportunities or just close off the area.

Forecast rationale

March temperatures are the biggest driver of our forecast for the cherry blossom peak bloom date, as they have historically been the best indicator. When it’s much milder than average in March, the blossoms tend to peak in mid- to late March; when it’s on the chilly side, they reach their prime in early to mid-April.

Last year, when the blossoms emerged unusually early, the March average temperature was more than 6 degrees above average. In 2019, the blossoms peaked on April 1, right around average, and the March temperature that year was also average. In 2014 and 2015, when we had back-to-back cold Marches, the blossoms peaked later, on April 10.

This year, we’re predicting March temperatures to be near to slightly above average, which is the primary driver for our forecast for a near-average bloom. The average temperatures for March’s first week will work out to around average before shifting to a warmer regime next week, with several days in the 60s to near 70. This should really get the buds moving.

To this point, due to the coldest February since 2015, the cherry trees have remained mostly dormant and have yet to even reach the first of five stages in the bloom cycle — the green bud phase, according to Leslie Frattaroli, a program manager for the Park Service.

“We are starting to see a few little green buds peek out, but nothing I would say is a majority of the trees,” she stated via email on Friday.

While next week’s warmth is likely to speed the bloom process forward, computer model simulations suggest the possibility of a cooler period in the third week of the month that could slow it down. Most models call for warming at the end of the month.

Unusually warm and sunny days, well into the 70s and 80s, combined with mild nights in the 50s and 60s, would really accelerate the bud progression, but there are no signs of this kind of warmth. But we also don’t see a strong signal for sustained cold weather and freezing nights, which would slow it down.

How the forecast could go wrong

If model simulations are flawed and it is either much warmer or colder than they are currently projecting, the peak bloom date may need to be adjusted. The March temperature forecast becomes more uncertain in the second half of the month.

Because the buds have been slow to emerge so far, if our blossom forecast is wrong we think it’s more likely peak that bloom will come later rather than earlier. Also, while we lean toward a mild end to March, one of the more reliable long-range computer models suggests it could be rather chilly.

Here are the odds of alternative peak bloom windows, outside our predicted range of March 30 to April 3:

  • Peak bloom March 25 or earlier: 5 percent
  • Peak bloom March 26 to 30: 15 percent
  • Peak bloom April 3 to April 7: 20 percent
  • Peak bloom after April 7: 10 percent

This peak bloom outlook is made on the basis of available weather forecast data in early March and we may revise it if big shifts in the forecast occur.

How have our forecasts done historically?

We have issued cherry blossoms forecasts since 2012 and have hit the peak bloom within our predicted window in five of nine tries.