Extra boats have been scheduled and all the beds are taken, as Herm basks in the sun.
Herm Island's Retail Manager, Becky McDonald, says the island's hotel and self catering cottages are booked out, and the campsites are busy.
"The island is completely full and it's wonderful to see all the visitors on the island.
"The French boats up from St Malo also help, and we've seen a big increase in French visitors over the past year."
"When the sun shines, everyone wants to come to Herm."
Becky says Travel Trident put on extra sailings to deal with the demand as the sun and heat combine with half term and a bank holiday.
She says most are respecting the island's natural beauty, but says people need to be cautious about causing a fire or leaving rubbish around.
"I did read a comment last night on a social media post about a group of people leaving their rubbish on Shell Beach and we'd appreciate people putting their rubbish in a bin, or taking it with them."
The four day heatwave is forecast to end later as cloudier conditions and a westerly breeze lower the temperature.
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