Thunder, lightning and heavy showers swept across France from west to east, knocking down sweltering temperatures and bringing an end to a over a week of unusually hot weather.

This year's heatwave was neither as hot nor as deadly as 2003's, in which 15,000 people died but it still put France's health system to the test.

The Institute of Health Surveillance said hospitals coped well with the influx of mainly elderly people in need of treatment for heat-related ailments.

"There was no malfunction, there was no saturation of the system," Gilles Bruecker, director of the institute told a news conference, adding that there was no mass transfer of old people from retirement homes to hospitals as there had been in 2003.

After the heatwave of 2003, France boosted measures to protect vulnerable groups, particularly the elderly, during unusually hot weather. This summer it issued advertisements advising the public to drink water and stay in cool places.

"We were not ready in 2003. That is obvious," Bruecker said.

Of the 64 deaths caused directly or indirectly by this heatwave, 40 were people over 75 years of age, although Bruecker said it was not always easy to say whether the unusual heat was responsible for their deaths.

Maximum temperatures on Thursday fell well below 30 Celsius (86 F) in many places where they had been in the low to mid-30s for a week. Forecasters said temperatures should remain closer to normal levels over the coming days.

In Spain, the heat brought a plague of jellyfish to country's eastern seashores, forcing holidaymakers to stay out of the sea, the Red Cross said.

The unwelcome visitors, which can reach the size of a dinner plate, have flourished thanks to a glut of plankton brought on by higher sea temperatures and a decline in natural predators like dolphins and turtles.

A power cut hit part of central London as faults and hot weather forced a supplier to cut off thousands of customers.

Lack of rain has also damaged crops. Drought caused Italian farmers losses of some 500 million euros (US$637 million) so far this year, hitting rice and maize producers in the north particularly hard, the main industry body said.