Advantage Travel Partnership said 18% of bookings within the past month were for August departures.
UK holiday companies are reporting a surge in last-minute bookings by people keen to escape poor weather at home.
Met Office figures suggest last month was the UK’s sixth wettest July on record.
Advantage Travel Partnership, a network of independent travel agents, said 18% of bookings within the past month were for August departures, up from an expected 4% at that time of year.
Chief executive Julia Lo Bue-Said told the PA news agency: “As a result of the UK’s poor summer weather, across our travel agency partnership we are seeing holiday sales for August soar, and reports of overseas heatwaves are doing nothing to dampen the desire for last-minute breaks.
“Availability is dwindling, particularly around the bank holiday weekend, but there are still some great offers around.
“Holidays for many people are sacrosanct, and after the last few years it’s the one expense that many families are reluctant to cut, even in the current economic climate.”
Holiday company On the Beach reported a drop in bookings during the UK’s hot weather in June, before a 7.4% rise in July when the majority of sales were for departures within two months.
Chief customer officer Zoe Harris said: “It’s no surprise to see our bookings increase during July, especially given the fact that we were treated to some classic, rainy, British weather.
“It looks as though holidaymakers have given up hope of a hot summer in the UK and instead have booked last-minute trips to find some sun abroad, with more than half of bookings made in July leaving in the next two months.”
Another online travel company, Thomas Cook, said more than 30% of the bookings it is receiving are for holidays this month, up from an expected proportion of 18-20%.
A spokesman said: “Bookings have continued to be strong throughout the summer as people wait until the last-minute.
“They’re getting some great deals, especially if they’re flexible with where they’re going.
“Mainland Spain – the northern coasts of Costa Brava and Dorada – are particularly popular.
“Greece has recovered back to second place for summer holidays.”