There are warnings for people to avoid swimming in lakes, rivers and other open water.
It follows the death of 17-year-old Russell O'Neill who lost his life over the weekend, swimming in a quarry near the Malvern Hills in Worcestershire.
Charlotte Grant reports.
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Any thundery rain or showers will quickly die away during the evening. Tomorrow, dry with long spells of sunshine and light winds.
Becoming dry with some late evening sunshine, then largely clear overnight. Tomorrow, a fresh start, though with plenty of sunshine.
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