Complex sentence: The heaviest rain fell in Shap, Cumbria, where 29 mm fell in 12 hours and both Lancashire and Yorkshire saw rainfall of 7--10 mm in the same period.
Split into simpler sentences: The heaviest rain fell in Shap, Cumbria, where 29 mm fell in 12 hours. Both Lancashire and Yorkshire saw rainfall of 7--10 mm in the same period.