Crowds of tourists and residents set off a flurry of selfie sticks and mobile phones in Tokyo's Ueno Park on Tuesday, as they flocked to enjoy the cherry blossoms marking the start of spring.

Japan had announced the season would start on March 21 with the flowering of sakura blossoms at the Yasukuni Shrine, but other places in Tokyo were denied the sight, because of a cold weather snap.

Tuesday's jump in temperature of 17 degrees C (63 degrees F), changed that, however, drawing out throngs of people for the "hamami” tradition of the viewing and appreciation of the famed pink flowers.

“It's very romantic,” said Gu Shuyi, a tourist from Beijing. "People say the petals of cherry blossoms are like snow, and I agree. I think it's very beautiful that we can see something like snow in warm weather, in a season of rebirth.”

Japan makes its cherry blossom predictions scrupulously, with one weather broadcaster collecting observations from 10,000 trees nationwide.

That is especially important for foreign tourists, who plan holidays to catch a glimpse. Japan's Tourism Ministry says the number of foreign tourists peaked in April last year, thanks to the popularity of the sakura flowers.

Beneath the flowering sakura trees, Tokyo residents laid out picnics, with some company employees arriving early to reserve places for colleagues still at work.

Monks marched down the paths of Ueno Park to the music of their flutes, as people rowed boats in the moat of the Imperial Palace.

Spring, it appears, has arrived.