May 20, 2023 – 7:31 PM
It is a difficult period for people with a grass pollen allergy. The highest grass pollen concentrations are expected between Wednesday 24 May and early July. Due to the warm and especially very humid weather so far this year, the grasses are looking good. This is good for the grasses, which therefore bloom profusely, resulting in high grass pollen concentrations. But less nice for people with hay fever complaints.
We are experiencing one of the wettest years to date. Completely different from the recent dry years. Ideal conditions for grasses to flourish. Pollen concentrations have been low for the past two weeks. Since the end of April/beginning of May, the two pollen counting stations, the LUMC and the Elkerliek Hospital have found a grass pollen concentration of 5 or more pollen per cubic meter of air in the pollen traps on their roof. Nevertheless, people with a grass pollen allergy have already experienced some complaints, because the amount of grass pollen in the air is higher at street level. The grass has also been developed locally.
Based on the observed and expected weather conditions, we expect the peak period of the grass pollen season this year to run from Wednesday 24 May to Saturday 1 July. If it is dry during that peak period, the grass pollen concentration can rise to several hundred pollen per cubic meter of air.
Precipitation during pollen peak is decisive
Grass pollen is one of the main causes of hay fever in the Netherlands. About 50% of people with hay fever experience complaints when exposed to grass pollen. From a pollen concentration of about 10 pollen per cubic meter of air, people who suffer from a grass pollen allergy will develop complaints. The higher the pollen concentration, the higher the level of complaints and the more people will also experience complaints.
The final amount of complaints experienced partly depends on the weather conditions when the grasses come into full bloom. That turned out last year. In the past summer, sales of over-the-counter hay fever medication were more than 22 percent lower than the year before. A very high nuisance peak due to grass pollen then failed to materialise. Just when the grass pollen concentration was about to peak, it turned out to be raining very hard. As a result, a lot of pollen washed out and people may have been indoors more often, so they were less exposed to the pollen.
The weather forecast from Weeronline will show warm, dry and fairly sunny weather in the coming days. This can increase the amount of pollen in the air. With a northeasterly wind, pollen can also be brought in from Germany. From Sunday, the chance of a local rain or thunderstorm will increase. This will keep the soil moist and keep grass thriving. Local showers do not bring real relief, because as soon as it becomes dry, more pollen will soon be released into the air again or they will be supplied from the environment.
Grass pollen forecast
During the grass pollen season, a daily hay fever forecast for the next five days can be viewed on the LUMC website. The expectation indicates whether the grass pollen situation is favourable, not so favourable, or unfavourable.
|Thanks to: Dr.ir. Arnold JH van Vliet, Wageningen University & Research; Letty de Weger, Leiden University Medical Center; Mieke Koenders, Elkerliek Hospital; Jaco van Wezel, Weeronline.