A band of rain followed by heavy showers is expected to pass over the Hertfordshire and North London area this afternoon and in to this evening. Some of these showers may be very heavy. In areas which receive the highest rainfall some localised flooding is possible, either from the rivers and or surface water flooding. The showers are expected to clear tomorrow morning. We will continue to monitor the situation.
See link below for more information
http://apps.environment-agency.gov.uk/flood/34681.aspx?area=062WAF28Pinn