Nic Lonsdale, duty watch manager at Portland Coastguard, said: "We are urging people to observe the warning signs and stay away from the edge." The cliffs at Durdle Door and Lulworth have been crumbling since the start of year.
In January, the steps to the famous landmark collapsed. Earlier this month, coastguards warned that the path was beginning to fall away.
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Drink lots of water, stay out of the sun during the middle of the day, and take particular care of vulnerable people.
Tuesday afternoon's weather for the east of the region