Thomson and First Choice parent Tui Travel will reveal how the holiday market has fared over the summer when it delivers a trading update on Wednesday.
The group said in May that summer sales were 13% ahead of last year as holidaymakers booked foreign trips amid fears of another washout season in the UK.
The recent heatwave came as an unexpected surprise and Tui will likely face questions over whether sales growth was affected in recent weeks.
Rival Thomas Cook last week said that around 85% of planned capacity is now sold for this summer.
EasyJet also defied concerns earlier this month that the hot weather hit last-minute getaways, saying almost three-quarters of its summer seats were booked.
Shore Capital analysts predict a similarly “confident” third quarter update from Tui.
“With around 80% of the UK programme sold at this juncture we expect the group to highlight it has fewer holidays left to sell, with margins and pricing ahead of last year,” the firm was quoted as saying.