The intensity of the pollen loads and the beginning and duration of the pollen season change from year to year according to the weather conditions before and during the pollen season. The rising temperatures of climate change are resulting in an earlier pollen season, and, in the case of certain pollen species, higher pollen loads.
Long-term monitoring of pollen data reveals changes in pollen patterns: early or delayed onset, intensification or amelioration of the pollen season, and the emergence of new allergenic pollen types, such as ragweed. MeteoSwiss measures and analyses the pollen concentrations in the air and identifies the changes in pollen patterns.
Pollen calendars show the average year-round profile of the pollen season for the major allergenic pollen types, and provide an overview at a glance of which pollen types are present when, during the course of the year. They aid in the diagnosis and prevention of pollen allergies. In Switzerland, the pollen season varies from region to region.