Hay fever sufferers are likely to struggle through this weekend's sunny weather, with high levels of pollen expected across England.
The pollen count will increase as temperatures heat up and the worst conditions are expected on Sunday and Monday, according to forecasters.
Alexander Burkill, of the Met Office, said tree pollen would be more significant than grass pollen until the middle of May.
People in the south east will be particularly badly affected while cooler temperatures in Scotland should lead to lower levels of tree pollen, according to Mr Burkill.
He said the tree pollen count will be high towards the end of the weekend, adding: "Today we've got a fair bit of cloud and the rain coming down, so it's going to go down to moderate.
"Onto Sunday and Monday in places, especially across England and especially in the south east, you're looking that it could get up to high."
South west England and Wales will only experience moderate levels of tree pollen on Monday, though Mr Burkill said those areas may see high levels on Sunday.
Regions with higher temperatures towards the south east of England will be worse for hay fever sufferers as warm weather leads to higher levels of both tree and grass pollen.
Grass pollen will still have an effect this weekend, according to Meteogroup, the weather division of the Press Association.
Tom Tobler, of MeteoGroup, said: "As we get more sunshine on Monday and it warms up in southern England, it could start edging into moderate pollen counts."
Mr Burkill said the much-anticipated warm weather would increase pollen levels. He said: "It's the fact that it's going to be mostly dry, quite warm and generally lightish winds across much of England and Wales."