Fall allergy season is getting worse

• Fall allergies can be particularly bad in cities, which are slightly warmer due to the urban heat island effect (the term for how paved surfaces and buildings retain and absorb heat). That added warmth allows pollen-producing weeds to grow for a longer period, per the NYT.
• Ragweed and mold from rotting leaves are often the culprits for autumn allergy symptoms, the newspaper reports.

Zoom in: The Asthma and Allergy Foundation of America recently named Seattle the least-challenging city for dealing with allergies — but that was based on the premise that it rains here, washing away the pollen and other irritants that aggravate symptoms.

• This year, it's been incredibly dry in September and October, providing allergy sufferers with little relief.

By the numbers: The state Department of Health says that, compared to 30 years ago, pollen season starts 20 days earlier and lasts almost a month longer — and that's mainly because of increasing temperatures from climate change.

What's next: Scientists predict there will be eight times as much birch pollen in our region by the end of the century, per the health department.