More than 150 schools are competing with Camelot by holding weekly "weather lotteries" - a gamble which centres on the English fascination with the climate.
Parents pick six numbers and win cash on any day when more than four match the last digits of the recorded Fahrenheit temperatures in Corfu, Istanbul, Tenerife, Innsbrueck, Edinburgh and Stockholm.
Each lottery ticket costs pound;1, of which 35p goes to the school. The rest goes to the prize-fund and the administrators.
Co-ordinators of The Great Weather Lottery scheme say the scheme has been popular with sports clubs for more than three years, but they have only recently started to target heads and parent- teacher associations.
One of the schools already involved is St Joseph's RC comprehensive in Bolton, where the lottery is providing a steady flow of cash to pay for a new minibus.
Senior maths teacher Linda Barlow said: "We like the lottery because it is no risk to us, and the parents like it because they know the school is benefiting."
But the system has appalled the Christian Institute, which is urging parents to donate money directly to schools. "It's a sad time for society when people have to win money to support something," said institute spokesman Iain Bainbridge.
Lotteries are the latest in a range of ambitious schemes being used by schools to raise cash for equipment or specialist status.
Parents at Mistley pre-school in Essex recently held a male strippers night for mothers, but had to cancel the lap-dancers for dads this month after press interest.