The emergency services were called to the first collision just after 0600 GMT on the slip road to the A21 northbound at Quarry Hill, Tonbridge.
Three cars collided in the tailback, followed by a third accident involving two cars. One man was slightly injured.
The road had to be closed for nearly three hours.
Insp Robert Ratcliffe urged drivers to adapt their driving to the road conditions.
"If there is rain the roads will be slippery and visibility poor.
"Drivers should keep their distance from other vehicles and allow sufficient time for their journey," he said.
Information courtesy of [BBC.co.uk]