A national emergency has been declared and much of England is covered in the Met Office's first-ever red warning.
"Please treat the warnings we are putting out as seriously as you would a red or amber warning for wind or snow, and follow the advice."
She told Sky News's Sophy Ridge On Sunday programme:"This isn't like a lovely hot day where we can put a bit of sunscreen on, go out and enjoy a swim and a meal outside.
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