Your London Pollen Forecast

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Local Pollen Information for London

Hay fever prevalence rates in London are as high or even higher than in the surrounding rural areas, despite central London's grass pollen counts being typically only 50% of those in the countryside. This is largely due to air pollution, especially from diesel vehicles. Photochemical smogs containing ozone and nitrogen oxides can exacerbate hay fever symptoms

Lower Pollen Count Areas in London

  • Central Urban Areas: While grass pollen counts are generally lower in the heart of the city, the high prevalence of air pollution can still make hay fever symptoms severe.

High Pollen Count Areas in London

  • Parks and Green Spaces: Areas like Hampstead Heath and Richmond Park, where grass is often left uncut, can have very high grass pollen counts.

  • Railway Banks: Railway banks with uncut grass create corridors of high pollen counts within the city.

The Pollen Season

Running from March to the end of September, the pollen season is split into three main categories

  • Tree Pollen - from late March to mid-May

  • Grass Pollen - from mid-May to July

  • Weed Pollen - from the end of June to September

Pollen Calendar Credit: The Met Office

Pollen is a very fine powder produced by the male parts of trees, flowers, grasses, and weeds to fertilize other plants of the same species. Many people have an adverse immune response when they breathe in pollen.

The immune system normally defends the body against harmful invaders, such as viruses and bacteria, to ward off illnesses.

Some peoples immune system mistakenly identify harmless pollen as a threat to the body and tries to fight it by releasing a chemical. We call this an allergic reaction, which can lead to a number of irritating symptoms such as

  • sneezing

  • stuffy nose

  • watery eyes

The Pollen Count

A pollen count is generated by measuring the number of pollen grains in a given volume of air, using a pollen trap.

What effect does time of day and weather have on pollen count?

Pollen counts tend to be higher in the early morning and late evening, although they can sometimes be high all day long.

If the grass is damp, the pollen peak will be later in the morning because the water evaporates before the pollen is released.

Some grasses release their pollen in the afternoon. Pollen rises in the air during the day and then descends at night, as the air cools.

In rural areas, the evening peak tends to occur between 6pm and 9pm but in the city, where the air stays warmer for longer, the pollen descends later and levels tend to peak between 9pm and midnight or even later, which is why you may wake up sneezing in the night.

Sunny days favour higher pollen counts and rain tends to wash the pollen away. On a cloudy day, pollen builds up only to be released on the next sunny day.

Pollen transported by bees Credit: ITV/MET OFFICE