Torrential rain started falling in the Medway area at around 6.40pm and continued for at least 35 minutes causing particular issues in Chatham.
Rain is forecast for 6am through 9pm on Tuesday, followed by a 90% chance of rain from 7am to 10pm on Wednesday and slightly more broken showers on Thursday.
Peterborough may be hit by flooding with the Met Office issuing a yellow weather warning.
Away from the warning areas, the rest of the United Kingdom should see more settled conditions, especially in parts of Scotland and Northern Ireland.
The Met Office's chief meteorologist Steve Ramsdale warned the weather conditions needed for heavy downpours and thunderstorms can happen "extremely quickly". Main threat from any stornger storms would be heavy rainfall.
"Winds may be strong in the west with the risk of coastal gales".
Rain, at times heavy, is expected today. Maximum temperature 14 °C. Minimum temperature 8 °C. High pressure finally settles by the end of the workweek, and dry, stable air will significantly limit any chances for rain Thursday and Friday. It is going to be more the persistence of the rain in some places and the intensity for others. The widespread rain this morning will turn more scattered this afternoon as a low pressure system travels over Kentucky and into Ohio.