At this time of year the flowers and plants are all in bloom and for most people this is the glory of summer and the promise of a good harvest in the Autumn.

But not for everyone, also at this time of year the grass pollen reaches its peak and hay fever sufferers are not so glad to see mid-summer.

The high levels of pollen in the atmosphere can cause misery.

When the forecast is a warm sunny one, the pollen index reaches levels of 5-8 and those that suffer wish for rain and cloudy days to wash the pollen out of the atmosphere.

About the pollen index

The pollen index season runs from the 1st April 2003 to 31st August 2003 and is supplied by the National Pollen Research Unit.

Bee collecting pollen

The pollen forecasts are made using information from the National Pollen Network, local vegetation, weather patterns in the winter and spring that influence grass growth, and the weather forecasts.

They can help hay fever sufferers to plan their activities and medication.

The index gives a level of risk to those that suffer. It is important to remember this is an index of the risk of being affected by airborne allergenic pollen and is not the actual pollen count.

During the spring months the main problem for hay fever sufferers is tree pollen.

Some types such as alder and hazel, can be in the air as early as January.

These are followed by elm, willow and ash in March. Pollen from these trees affects only a small percentage of hay fever sufferers but can cause symptoms in some allergic people.

The pollen from silver birch trees is the most important tree pollen type for hay fever sufferers and usually occurs in April.

This pollen type affects about 25% of hay fever sufferers. The season usually lasts for about four weeks and counts will be high on dry, warm days with some wind in areas where there are birch trees.

The birch tree pollen season is followed by the oak tree pollen in late April and early May, although oak affects fewer sufferers than birch.

The most important pollen type for hay fever sufferers in the UK is grass pollen.

This season starts in late May and continues through to mid August, with the main peak occurring usually in June and a second smaller peak typically occurring in early July.

About 95 % of hay fever sufferers are allergic to grass pollen.

The amount of grass pollen in the air can differ a lot from day to day and even within days depending on the weather.

Weed pollens affect a small amount of sufferers from June to September with a peak in August.

The pollen index changes emphasis slightly during the season to reflect the predominant types of pollen.

Tree pollen forecasts:
from 01/04/03 until 22/05/03
Grass pollen forecasts:
from 23/05/03 until 08/08/03
Weed pollen forecasts:
from 09/08/03 until 31/08/03

First published: 13 June 2003