People gather at Stonehenge in England on Saturday to celebrate the summer solstice, the longest day of the year. ALBERTO PEZZALI/AP

Europeans are braced for a heat wave that could push the mercury beyond 44 C this week, and cost the lives of elderly residents and people with underlying health conditions.

The heat wave, which is centered on France but that is impacting much of Western Europe, has prompted the French government to put its emergency services and military forces on high alert, with teams ordered to be ready to attack heat-related wildfires.

The average temperature in France at this time of year ranges between 15 C and 25 C.

The country has also canceled some outdoor sports events, and restricted alcohol availability at a major nationwide music festival on Sunday, over fears people could become dehydrated by drinking beer to stay cool, instead of more appropriate beverages.