The fire service said they are responding to a number of flash floods in Worthing, Littlehampton and Adur.
At around 2pm, the heavens opened and the area experienced extremely heavy rain.
Littlehampton was also affected, with the A259 and residential roads being flooded with water and with poor visibility while driving.
And now, the A27 is partially blocked due to a tree which has fallen on the A27 in Crockhurst Hill at the junction with Mill Lane, near Durrington Cemetery.
The combined effect of these floods means that drivers can expect delays in the Worthing, Littlehampton and Adur areas while the flooding subsides.
West Sussex Fire and Rescue Service tweeted to say: “We’re busy responding to a number of flash floods in the Littlehampton, Findon & Worthing areas after downpours. Our priority to protect people’s homes and possessions.”