Pollen Count in Leiden

4-Day Chart
Annual Overview

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Trees start making pollen in Leiden in February. This is the start of pollen season. It begins with alder, hazel, and elm trees. They release tiny amounts of pollen into the air.

Updated: 3/21/2026

In March, more trees start making pollen. This includes oak, birch, and beech trees. They add to the amount of pollen in the air. The pollen count gets higher.

In April and May, grasses and weeds start making pollen. This is the peak of pollen season. The air is filled with pollen from trees, grasses, and weeds. It's a difficult time for people who react to pollen.

In June, pollen season starts to slow down. The amount of pollen in the air gets lower. By July, pollen season is almost over. The air is cleaner, and it's easier to be outside.

Pollen Forecast Chart

Recommendations

When pollen concentrations reach a peak, we suggest these simple steps to help with hay fever. These tips are extra important on windy days when plants are in peak anthesis (the time when they release the most pollen).

Wear masks if necessary
Shower after going out
Wear sunglasses if windy
Close windows and doors
Use an indoor air purifier
Avoid wearing woolen clothes outside
Limit outdoor activities

Annual Pollen Overview

Check out this month-by-month overview of the daily average pollen count in Leiden 🌾. This data is based on previous years and serves as a guideline to help you understand when different pollen seasons typically occur in your city.

	Alder	Birch	Grass	Mugwort	Olive	Ragweed
Jan	0	0	0	0	0	0
Feb	9.6	0	0	0	0	0
Mar	171.2	12	0	0	0	0
Apr	6.7	801.8	15.3	0	0	0
May	0.7	126.5	74.8	0	0.1	0
Jun	0	0.1	565.6	29.5	0.2	0
Jul	0	0.7	214.4	151.1	0	0
Aug	0	0	81.8	41.6	0	0.3
Sep	0	0	14.5	1	0	1.6
Oct	0	0	1.6	0.1	0	0
Nov	0	0	0.2	0	0	0
Dec	0	0	0	0	0	0

Nearby Places

Disclaimer * The pollen count information provided for Leiden is for educational purposes only, sourced from the CAMS European air quality database. We cannot guarantee its accuracy or reliability. This information is not a substitute for professional medical advice. Consult a qualified healthcare provider for medical concerns. We are not medical professionals.