Hay fever sufferers are being warned to brace themselves for symptoms with drier weather set to trigger a peak in pollen levels.
Forecasters are predicting that more settled conditions will bring a high to very high risk of pollen affecting much of the country from Thursday and into the weekend.
Dr Beverley Adams-Groom from Worcester University, the UK’s chief pollen forecaster who advises the Met Office, said recent rainy weather had delayed the impact of the grass pollen season, which usually begins between the end of May and start of June.
“We’re right in the season now, the grasses have been ready to emit their pollen properly and fully for a week or so now,” she said.
“We’re going to see the full peak coming up over the next week or so now.”
She added: “This year we’ve seen a rather stumbling start to it, the rain has dampened down the grass and prevented it from emitting their pollen.”
Dr Adams-Groom said the main grass pollen season can affect up to 95% of hay fever sufferers, adding that conditions were not out of the ordinary.
“From now on, certainly for the next three days, we’ve got high to very high risk for quite a lot of the country,” she said.
“It’s nothing exceptional, forget all this stuff about a pollen bomb, it’s what we would normally expect to see.”
Grahame Madge, a spokesman for the Met Office, said the pollen risk on Thursday was high in most of England and Wales and medium in Scotland.
This is expected to move to very high across England, Wales and Northern Ireland and high in southern Scotland by Saturday.
“When you get settled weather and dry conditions, that will allow pollen to become airborne and remain airborne with the obvious impact on sufferers,” Mr Madge said.
Forecasters are expecting largely clear skies for much of the country from Thursday to Saturday, with a risk of isolated showers, particularly in Scotland.
Temperatures in London and the south east will be around 21C or 22C on Thursday, with the warmer and more settled conditions lasting across much of the country until Saturday.
Mr Madge said a “plume of very warm warm air coming up from Europe” will see temperatures soar from Sunday and into early next week, but also bringing a risk of thunderstorms in the south-east and east.
The mercury could rise to the high 20s C in parts of the south and east, and possibly touching 30C in isolated areas.
Temperatures are expected to fall again if thunderstorms do strike, but Mr Madge said the forecast is currently uncertain.