As the days gradually get longer and the weather warmer, the traditional spring sounds are being drowned out by unseasonal sneezing and sniffing.

The early arrival of hay fever each year is one of the unforeseen effects of global warming.

This is because, in response to changing temperatures, many flowers, including tree and grass flowers, are blooming earlier and for longer.

This means pollen is being released for longer periods than before and because 95 per cent of hay fever is triggered by grass pollen, it means hundreds of people across Sussex are facing months of misery.

According to the Woodland Trust conservation charity, in some parts of the country, mowing the lawn has become a constant, year-long chore.

Although cut grass is usually too short to flower, sap allergens released by it add to people's woes.

This spring, the trust and the National Pollen Research Unit are asking people to record the early-flowering grasses, such as meadow foxtail and Timothy grass, as part of the UK Phenology Network's survey, which is monitoring the timing of natural events in a changing environment.

Woodland Trust supporter and Met Office senior broadcast meteorologist, Michael Fish said: "Higher temperatures are extending the grass-flowering season.

"Like me, many more people will be condemned to longer bouts of sneezing, itchy eyes, headaches and a throbbing nose."

"Information collected by amateur phenologists throughout the UK - who record naturally-occurring seasonal events in gardens, parks, woods and high streets - will help to forecast the start of the pollen season."

Professor Jean Emberlin of the National Pollen Research Unit said: "Last year, the grass pollen season was exceptionally long because the weather was wet and warm.

"The season extended into August, instead of ending in July."

Generally, hay fever is affecting more and more people. Numbers have risen since 1965, when between ten to 12 per cent of the UK population was affected.

Nowadays, the figure is between 15 and 25 per cent in the population as a whole.

While grass pollen is the most common trigger, birch pollen is important, too.

The birch pollen season has been occurring five to ten days earlier per decade in the past 30 years.

The Trust wants people to let it know when they see trees and grasses beginning to flower.

This will give the Trust vital information about flowering times in advance of pollen release and help improve forecasting for the start of the pollen season.

This will ultimately help people take their medication at the right time.

Hay fever is one of the most common allergies in the UK, affecting about 12 million people.

It is a modern disease and was virtually unknown before the 1800s and it became more widespread during the last century. Common symptoms include a runny nose, itchy eyes, a sore throat and repeated sneezing attacks.

This happens because of inflammation in the mucous membranes of the nose and eyes, triggered off by a sensitivity to one or more species of pollen or fungi.

In addition, many patients with hay fever develop other allergic conditions such as asthma and sinusitis.

Several steps can be taken to limit the damage.

These include letting someone else mow the lawn or do the gardening, shutting windows and doors in the house and closing the sunroof and windows in the car when the pollen count is high.

Pollen levels tend to peak mid-morning and early evening so people are urged to try to avoid going out at those times.

Sufferers can also wear sunglasses with wraparounds that sit close to the face - these prevent pollen getting into the eyes.

Symptoms can also be relieved with antihistamines and decongestants, which reduce sneezing and help a watery, itchy nose as well as improving nasal congestion.

There are also a number of homeopathic remedies available for people not keen on taking prescribed drugs and steroids to control their condition.

A simple recording form for marking the signs of spring growth is available from the Woodland Trust on 0800 083 7497 or by logging on to www.phenology.org.uk