When the cherry trees come alive in their explosion of pink, millions of Japanese hit the parks for one of this country's biggest outpourings of merrymaking.
So, Japanese are impatiently asking, when will it all start?
Very soon, officials say — thanks to global warming, the Tokyo area is having one of its earliest cherry seasons ever.
According to predictions released by Japan's Meteorological Agency, the trees are expected to bloom as early as this weekend in the capital area, where about a quarter of all Japanese live.
That would be 10 days earlier than average and the second earliest since the agency started compiling data in 1953. The earliest on record for Tokyo is March 16, 2002.
"Cherry blossoms bloom earlier in relation to a rise in temperature, and this temperature increase is related to global warming. So there is an indirect connection," Hiroko Morooka, a Meteorological Agency official, said Tuesday.
With countless parties to be planned, including a bash hosted by the prime minister with 10,000 invited guests, predicting when the brief cherry blossom season will occur is a major concern.
Newspapers and television networks track the blossoms' march — called the "sakura zensen" or cherry blossom front line — from the hotter southwest of the country through chilly Hokkaido in the north.
When the blossoms open, offices clear out, friends gather, families picnic.
Because of unusually warm weather in recent months, this year's blossoms have been watched particularly closely. Park officials, who have to be ready for the crowds, are worried.
"It's difficult to predict this year since it's been warm all winter," said Toshiharu Kobayashi of the Tokyo Metropolitan Park Association. "Usually, the temperature drops and then hikes up for the cherry blossoms to bloom, but this year, it's been warm all along."
The biggest draw is Ueno Park, where 2.3 million people are expected during the blossom season.
Even in the best of years, cherry blossoms are notoriously short-lived. Temperature changes and even a day of rain can considerably cut their longevity, which is usually only about a week.
To hedge his bets, the prime minister's party is held at a Tokyo park with a hardier variety of cherry that blooms later and lasts longer. The party, attended by celebrities, business leaders and the political elite, is scheduled for April 14.
The early blooms underscore a significant change in Tokyo's climate.
The average temperature during winter months in Tokyo from 1971 through 2000 was 44 degrees Fahrenheit, according to the Meteorological Agency. From December 2006 to February 2007, the average temperature was more than 3 degrees higher — 47.5 Fahrenheit.
Residents say they have noticed the change.
"Global warming has become more of a personal reality for me," said Tomoko Yokoyama, a 37-year-old Tokyo housewife. "It seems like everything is happening earlier. I haven't seen any snow, and the hay fever situation is worse for my daughter."