The Met Office has predicted a washout in London on Bank Holiday Monday, with strong winds forecast throughout the afternoon and night.
A yellow weather warning for wind across much of the south coast of England and coastal Wales covers Monday and Tuesday, with the strong gusts predicted to cause travel disruption.
Forecasters also warned that people socialising could see temporary structures blown away by gusts of up to 40-50mph if they are not secured properly.
Met Office meteorologist Craig Snell said Saturday and Sunday will continue to be cold for the time of year, with sunshine and scattered showers.
He said temperatures will be around 13C to 14C in the south over the weekend, below normal temperatures for this time of year of closer to 16C.
Monday will see much more widespread rain of up to 40-50mm alongside strong winds, he added.
He said: “Monday will see a bright start in the east.
“Rain will be moving in from the west in the morning and spread to all parts over the course of the day. The rain will be accompanied by strong winds.
“It will be blustery for everyone but especially the south coast where we do have a yellow weather warning.
“Expect some localised transport disruption and tents and temporary structures could be liable to be blown away if they are not secured properly.
“It will be a wet and windy day for some of us and remain quite cold.
“In that weather warning area we could see gusts of 40-50mph, maybe even up to 60mph.”
Meanwhile the Metropolitan Police have warned people to stick to the rules when going out over the weekend and avoid attending planned protests in London.
The force said it will have a “significant policing operation” in place.
The Met Office said that going into next week and towards polling day on Thursday the weather will return to a mixture of sunshine and showers.
Mr Snell added: “Going into next week we get rid of this area of low pressure around early Tuesday and go back to where we are now, a cold flow from the north with a mix of sunshine and showers.
“In the south we might well see another band of rain coming in from the south west so it might be a bit more gloomy and wet in the south of the UK but it’s a little bit uncertain.”