The rain showers also did little to help firefighters battling persistent wildfires across southern Europe, with a new rash of blazes raging in Portugal and Spain, forcing hundreds of residents to flee their homes.
With 40 deaths already attributed to both the unrelenting heat and the spate of forest fires in Europe, a top French emergency doctor warned of an impending crisis, saying dozens could succumb to the heat in the coming days.
After a prayer from Pope John Paul II for rain, isolated showers on Monday hit parts of France and Britain, which on Sunday registered its hottest day ever, and its first day above 100 degrees Fahrenheit (37.8 Celsius) since records began.
The thermometer in Gravesend, southern England, hit 38.1 degrees Celsius (100.6 Fahrenheit) -- an uncomfortable reading that large parts of Europe have had to tolerate for more than a week.
Forecasters predicted that the searing heat wave could continue for the rest of the week, sending tourists flocking to beaches across Europe's shores and leaving many office employees grumbling about sub-par working conditions.
Authorities in the Netherlands have issued a code red alert for possible power shortages, the first in nearly a decade, with residents urged to limit electricity consumption on Monday.
In France, where officials were meeting Monday to discuss the possibility of power rationing, the head of the country's association of emergency doctors said deaths among elderly people had skyrocketed in recent days.
"In the last four days, there have been practically 50 deaths due to the heat," Patrick Pelloux told television station TF1 -- a claim rejected by the national health service, which said no accurate statistics existed.
At least 20 people are known to have died in Europe due to heat-related illnesses in the past 10 days -- 19 in Spain and a three-year-old girl who died of dehydration in her family's car parked at their home in northern France.
Another 20 people have been killed in forest fires -- five in France and 15 in Portugal, where more than 300 firefighters on Monday battled to control a blaze in the Monchique mountains in southern Portugal.
Three water-dropping Canadair planes, two helicopters and a contingent of Portuguese troops were to be deployed to help weary fire brigades, who feared that rising temperatures would complicate their task.
On Sunday, fast-moving blazes forced emergency workers to evacuate several hundred people in Marmalete in Portugal's southern Algarve province, as well as 500 others in Spain's northeastern Catalonia region.
The forest fires in Croatia, France, Italy, Portugal and Spain have ravaged more than 200,000 hectares (500,000 acres) of pinewood and brush in the past two weeks, most of it in Portugal.
Authorities in Lisbon estimated the rash of blazes had caused damage totalling at least 925 million euros (1.05 billion dollars).
The heat wave has been caused by an anticyclone which has anchored itself firmly over the west European land mass, holding off rain-bearing depressions over the Atlantic and funnelling hot air north from Africa.
The hot weather, combined with months of severe drought, has left Europe's farmers in dire straits: an official for one of Spain's main farmers' unions said losses in the country's agriculture sector could total 800 million euros (900 million dollars).