Grey clouds, wet weather and heavy thunderstorms will dampen the bank holiday weekend for many, with yellow warnings in place from midday on Sunday. Although Saturday will remain largely dry and bright, with temperatures reaching as high as 22C in London and south-east England, the late May bank holiday could end in a washout, with “scattered, heavy and thundery downpours” predicted by the Met Office. A week ago, weather forecasters were predicting a mini-heatwave across the UK over the bank holiday weekend, with highs of 30C in south-east England. But those expectations appear to have cooled along with the weather. Those heading to the Birmingham Pride festival on Sunday will have to put up with patchy rain and the chances of heavy scattered showers, thunder and gusty winds increasing as the day goes on. Conditions are expected to deteriorate on Saturday night for most of the UK, starting in Cornwall and East Anglia, and bringing persistent rain right across the country. On Sunday morning, showers are predicted to break out so frequently that the Met Office is warning up to 40mm of rain could fall. “If that does fall where the ground is already well saturated from this week’s rainfall, we could see some localised impact – perhaps some spray on the roads – so do take care if you’re out and about, particularly through Sunday,” said the Met Office meteorologist Annie Shuttleworth. The yellow thunderstorm warning will last until Sunday evening, covering large swathes of England and northern Wales. There may be some frequent hail and lightning strikes. Flooding, power cuts and travel disruption are also possible. Monday will feel even cooler and breezier, with north-west England and south-west Scotland all expected to see scattered showers. Drier conditions are possible in parts of Wales, Northern Ireland and south-west England in the afternoon, but heavy and thundery downpours are expected across eastern parts of the UK. Further wet weather is predicted across the half-term, when many families will be taking a week-long holiday. The Met Office forecaster Craig Snell said: “Overall, it’s a pretty mixed picture. Saturday’s probably the best of the bunch. There will still be some sunshine around on Sunday and Monday, but we’ll certainly be dodging downpours. “Watch out for some thunderstorms, especially across parts of northern and central England and north-east Wales too.” Yellow warnings for rain have been in place in many parts of the UK throughout the past week and a 10-year-old girl, Leah Harrison, was killed in a mudslide during a school trip in North Yorkshire on Wednesday during heavy rain.