More than 200 pupils at St George's Preparatory School in Jersey were due to have a day at the beach in July.
But after hearing a health department warning about skin cancer on the island, headmaster Colin Moore said the school would be organising "a less exposed alternative event".
Mr Moore said "the children's health must take priority".
He said the decision was made with "considerable regret".
"I'm not suggesting we shouldn't go to the beach... but I think there is a big difference between taking your family to the beach and 210 or 220 children."
He said the school may "resurrect" its visit to the beach in future years if adequate shading is available.
The average Jersey temperature in July is 14C to 20C, compared with 11C to 19C in the UK, according to the Met Office.
Too much sunshine was also blamed for the closure of an outdoor swimming pool in Cornwall because lifeguards were unable to clearly see the bottom of the pool after the weather helped create an algal bloom.

Ashley Talbot, 15, died at Maesteg Comprehensive School in December 2014 after a crash with a minibus driven by a teacher as the school day ended.
The girl said she saw Ashley run between two buses with a friend before the collision happened.
Teacher Chris Brooks was questioned by police but no action was taken.
About 1,000 children were leaving the site in Bridgend county on foot, in buses or cars. On Monday, the jury was told there was regularly "major chaos" outside the school.
The inquest in Aberdare heard the girl had been on a different bus waiting to leave when she saw Ashley with a single earphone in his ear.
She heard three beeps from a vehicle and then saw  Ashley run between the buses before colliding with the minibus.
She said he was thrown onto the bonnet and landed on the floor before the wheel went over him.
Mr Brooks got out of the minibus and ran to the back of it and then to the school to get help. Teachers and bus drivers attempted to give first aid.
She said in a statement she had previously witnessed five near-misses when children had been moving between buses, causing cars to beep and brake.
Other children gave statements saying they had been involved in near-misses but had not reported them because they did not consider them to be serious enough.
Many pupils reported seeing Ashley running with his friend towards the buses on the day he died.
Ashley's friend, who was injured by the minibus, said in a statement he saw it "one or two seconds" before he was hit but could not avoid it and had only heard the engines of the buses which were "quite loud".
He saw Mr Brooks looking ahead and driving at around 10mph.
He felt he and Ashley were to blame for the collision and they should not have been running, adding they had been taught when they were young to "stop, look and listen".
He said they were both racing to get a seat at the back of the bus.
Another child who was on the minibus described seeing Ashley being hit and go underneath, while another passenger described it as feeling like "driving over a speed bump".
One child said in a statement that he had "nearly been knocked over twice at the same location".
He said he had been crossing the road between the buses when a minibus was coming towards him but did not report it because "such occurrences happen nearly every day"
A female pupil told the jury in a statement that she and a friend had nearly been knocked over by a taxi at the same location a couple of weeks before Ashley's death.
However other pupils said they had not been involved in near misses, and they had received instruction on road safety when they joined the school.
The inquest is continuing.

Petra Atkinson, 42, died in hospital after what Humberside Police described as a "domestic incident" at a property in Heather Avenue, Withernsea.
Tony Jobling, of Heather Avenue, appeared at Hull Magistrates' Court charged with murder.
Mr Jobling was remanded in custody to appear at Hull Crown Court on 8 September.
The cause of death has not yet been revealed.
A school's annual beach day has been scrapped over concerns about the dangers of midday sunshine.
[NEXT_CONCEPT]
A girl who witnessed the death of a teenage boy hit by a minibus at his school has told his inquest she had previously seen five near-misses.
[NEXT_CONCEPT]
A 51-year-old man has appeared in court charged with murder following the death of a woman in East Yorkshire on Sunday.