The Netherlands may be enjoying some early summer weather but the air quality is currently poor, thanks to a combination of pollution, birch tree pollen and sand from the Sahara, says weather bureau weeronline.nl.

The south to southwesterly winds are bringing in air pollution from Belgium and Germany’s industrial Ruhr district, which is adding to domestic pollution from cars, weeronline.nl says.

The dust from the Sahara desert, which can be seen in the brownish glow on the horizon, is making the air quality worse, experts say. And hay fever sufferers are being hit by birch pollen, which is earlier than usual this year.

The warm, sunny weather will continue into Thursday but there may be thunderstorms on Thursday evening which will improve air quality, the weather bureau says.

Rain and sea winds are also expected at the weekend.

Caterpillars

Meanwhile, the first Oak Processionary moth caterpillars have been spotted, the earliest date recorded, experts in the pest said on Wednesday.

They are advising local councils to start taking measures to combat the caterpillars, which shed poisonous hairs that cause skin irritation and breathing problems, as early as next week.

The warm weather means the caterpillars are likely to start shedding their hairs well before the first week in May.