The Met Office has warned of flash floods, lightning, hail and gusty winds in Sussex at rush hour today as it upped its weather warning from yellow to amber.
In a statement, the Met Office said: "An area of thunderstorms across northern France is expected to move across parts of southeast England during this evening's main travel period.
"The main hazard is likely to be heavy rain with 30-40mm likely in one to two hours which may lead to flash flooding.
"Lightning, hail and gusty winds are also expected which may cause power cuts and travel disruption."
Drivers are being warned that spray and sudden flooding could lead to difficult driving conditions and some road closures and that where flooding or lightning strikes occur, delays and some cancellations to train and bus services are likely.
It has also said power cuts are 'likely to occur' and other services to some homes and businesses could be lost.
The Met Office added: "Flooding of homes and businesses is likely and could happen quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds."READ MORE: This is why Japan’s bad weather will impact the UK this week