The Met Office has warned of heavy rain today across south west Hertfordshire.
They have issued a severe weather alert, warning of the possibility of localised flooding and disruption to transport.
The yellow alert is the lowest level of severe weather warning, and asks members of the public to "be prepared for adverse weather".
A flood alert has also been issued for Upper River Colne and Radlett Brook at London Colney, Colney Heath and Radlett.
The Met Office’s chief forecaster said 15mm of rain could fall in a short time.
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