Forecasters have warned there is “a lot of uncertainty” for the weekend’s weather outlook – with the biggest chance of showers coming when two major outdoor events are to take place.

Norwich-based Weatherquest said that while Suffolk and Essex were likely to start the weekend with warm weather and hazy sunshine, the situation was likely to go “rapidly downhill” throughout the afternoon.

Weatherquest’s Dan Holley said Saturday morning would be mainly dry, though some light rain from overnight may remain to begin with.

“It will probably feel quite warm and humid,” he added.

“Then, throughout the afternoon it’s likely to start clouding over and by the evening we’re likely to see some outbreaks of rain.

“There’s still lots or uncertainty as to when the rain will happen but as we go on the risk increases each hour.

“It could be quite a wet evening.”

The outlook could be bad news for St Elizabeth Hospice’s Midnight Walk, which sets off from Trinity Park on Saturday night, as well as the Twilight 5km run earlier that afternoon and evening.

However, while there have been reports of heavy thunderstorms hitting the country, Mr Holley said there was unlikely to be more than “the odd rumble of thunder”. And despite the chance of rain, temperatures are expected to reach 17-19C, possibly even highs of 20C.

Sunday is expected to see the weather improving as the day goes on, as overnight rain makes way for a largely fine afternoon.

High temperatures of 15-18C are expected.

By Monday, the weather front that brought the rain is expected to return, but Mr Holley said it would be “much weaker”.