Cherry blossoms across Japan have bloomed six months early after two powerful typhoons pummelled the country in September, stripping leaves, bringing a warm snap and turning the trees unseasonably pink.

"We get reports every year of cherry blossom blooming early, but those are confined to specific areas," Toru Koyama, a senior official with the Flower Association of Japan, told Reuters.

"This time we are hearing about it from all over the country."

The two typhoons, including the most powerful storm to hit Japan in 25 years, weakened chemicals that suppress the pink and white blooms by stripping the leaves or covering them in salt water, Koyama said.

Air sucked up by the storms from the tropics then brought warm weather followed by colder temperatures that mimicked the spring weather that signals the right time to bloom.

As yet, the number of flowers blooming early is still small, so people who go to view the cherry blossoms in spring, a huge draw for families and tourists alike, are unlikely to notice much difference, he added.

The unexpected bloom comes amid growing concern around the world about global warming and summer heat waves that are triggering intense forest fires and powerful super storms fuelled by rising sea temperatures.