N nd summer has only just begun

conditioned casinos, and some tourists lugged packs of bottled water around the Strip.

Phoenix has hit 49C only three times in recorded history. The record high was 50C on June 26, 1990.

The weather comes as new research found that nearly one in three people now experience 20 days a year when the heat reaches deadly levels.

The study of nearly 2000 deadly heat waves worldwide since 1980 was published on Tuesday in the journal

In the Southwest US, the heat has caused several problems this week.

In addition to grounding more than 40 flights of smaller planes, airlines have been taking other measures on larger jets to reduce their weight.

American Airlines spokesman Ross Feinstein said the carrier began limiting sales on some flights to prevent the planes from exceeding maximum weight for safe takeoff in the hot conditions.

Picture / AP ada because of the heat.

Construction workers in Phoenix took shelter from the sun where they could find it, while pets also got a bit of protection from the heat.