The willow and poplar catkin season is arriving earlier than usual across northern China and the Yellow-Huaihe River Valley this year, with floating fluff expected to linger through much of April, heightening fire and allergy risks.

Weather China, a website affiliated with the China Meteorological Administration, said the annual catkin dispersal began a day or two earlier than last year as temperatures rose to around 20 C across the region.

In Beijing and Tianjin, for example, the season is set to start between Monday and Thursday. Driven by warm, dry and breezy conditions, the two cities are expected to see peak levels of poplar and willow fluff from mid-April.

The catkins, which can blanket North China and the Yellow-Huaihe River Valley well into May, are more than just an allergy trigger — they also pose fire risks, the website said.

What floats in the air each spring is not a flower but the tiny seeds of poplar and willow trees, carried by fluffy white fibers, it added.

While the fluff itself is not the primary allergen, it can carry pollen, dust and fungi, triggering allergic reactions such as sneezing, runny noses and itchy eyes.

Li Yuan, deputy chief physician at the China Meteorological Administration Hospital, advised the public to take daily precautions during periods of high pollen levels.

She recommended wearing a tightly sealed mask and protective eyewear, such as goggles or wide-frame sunglasses, to reduce exposure. Once indoors, rinsing nasal passages with saline and washing the face and eye area can help ease irritation.

Weather China advised avoiding outdoor activities between 10 am and 4 pm, when catkins are most abundant. Those with asthma or severe allergies are urged to steer clear of areas with dense, drifting fluff.

Poplar and willow catkins are highly flammable due to their oily fibers and large surface areas. When exposed to an open flame, they can ignite and burn rapidly. Experiments show that a 1-square-meter patch of catkins can be engulfed in flames in under two seconds, quickly spreading fire to nearby grass, vehicles or even buildings, the website said.