Temperatures hit 6C over the Easter bank holiday and peaked at 8C on Tuesday afternoon.
Jonathan Hobbs, who owns boat operator Hobbs of Henley, said he had hired out dozens of self-drive boats over the weekend.
He said: “The best thing for us is that the river is safe to go out on. We’re praying for a decent summer after a wet winter and a wet summer last year.”
Gary Connery, who runs the Chocolate Theatre Café in Thames Side with his wife Vivienne, said he had served his highest number of customers this year over Easter.
He said: “It’s hard to say whether it’s because of the sunshine. Us Brits are used to unpredictable weather and we put up with it whatever it does.” On Wednesday, families played with their children and walked their dogs on Mill Meadows in Henley.
Despite slightly cloudy skies and a cool breeze, many were enjoying their first ice creams of the year.
This week’s sunshine follows a sudden cold snap in the last two weeks of March. The weather station at RAF Benson recorded lows of -1C on the weekend of March 23 and 24 and snow fell on that Saturday.
Temperatures are expected to continue rising next week, with highs of 14C predicted by Thursday. There will be some rain in the first half of the week.