An unusually severe surge in hay fever symptoms is affecting millions across England as a “pollen bomb” triggered by this year’s unpredictable weather combines with a forecast heat wave. The Met Office has predicted very high pollen counts for much of the country starting today, coinciding with temperatures expected to reach as high as 34°C, with a chance of breaking June’s historical record of 35.6°C set in 1957.

This year’s hay fever season has been disrupted by an irregular weather pattern marked by a warm, dry spring that encouraged vigorous plant growth, followed by a period of cold and wet conditions. This sequence delayed the flowering of trees but nourished abundant grass growth. The recent return of warm weather has caused tree and grass pollen production to spike simultaneously, compressing what is usually a staggered pollen season into a single intense period.

Alastair Culham, a botanist at the University of Reading and a long-time hay fever sufferer, described the convergence of high levels of both tree and grass pollen as a “perfect storm.” While some individuals are sensitive to only one type of pollen, those allergic to both are experiencing particularly severe symptoms. Culham noted that this year’s outbreak has been the worst he has endured in several years.

Typically, the hay fever season begins with tree pollen from late March through mid-May, followed by grass pollen lasting until July, and finally weed pollen from late June through September. However, the recent weather conditions disrupted this pattern, causing overlapping pollen releases. Certain tree species, such as hazel and oak, have completed their cycles, but lime trees—prevalent in urban landscapes—are currently at peak pollen production. These trees, known for generating large amounts of pollen, have thrived due to the combination of earlier warmth and recent rainfall.

Health officials have warned sufferers to use caution with antihistamine medications, especially if driving, due to potential drowsiness. Duncan Burton, England’s chief nurse, advised against exceeding recommended doses to avoid impaired alertness on the road.

The unusual pollen activity is exacerbating symptoms such as itchy eyes, headaches, and blocked sinuses, leading to a doubling of visits to the NHS hay fever advice webpage in recent days. Approximately one in four adults and one in eight children in the UK experience allergic rhinitis, the clinical term for hay fever.

Scientists have also linked the lengthening and intensification of pollen seasons to climate change. A study published earlier this year involving 65 researchers worldwide reported that global warming has extended pollen seasons by about two weeks since the 1990s, potentially worsening allergic reactions for sufferers in the future.