A heat wave that has broken records across the western United States is expected to worsen over the next few days. Temperatures have broken records across much of the western half of the country, with a high of 115 in Las Vegas and 119 in Phoenix on Saturday. San Antonio, Texas reached 108, a record for that city. Death Valley temperatures hovered around 124. The highest temperature ever recorded on Earth was 134, recorded in July of 1913 in Death Valley.
In recent weeks, the Northern Hemisphere has experienced unusually violent and changeable weather due to a double jet stream phenomenon, with a weaker jet stream circling the arctic while a stronger one dipped south. At one point last week, it was hotter in Anchorage than it was in Miami. Throughout the summer, warm moist air colliding with unusually cold air in the mid and upper latitudes of the region has caused almost continuous violent weather across the center of the continent, including severe flooding in places as far apart as Calgary and South Texas.
Authorities are worried that temperatures may go higher next week, reaching into areas where they pose a health hazard especially for young children and the elderly. Power systems across the region are being stretched to the limit, and if the heat increases, controlled brownouts or outright power failures will be likely. The highest temperature a human can safely endure varies depending on the age and health of the individual and the amount of humidity involved. In general, the higher the humidity, the lower the safe temperature. Under present conditions, temperatures above 120 will become dangerous for infants and elderly people who do not have access to air conditioning. Above 115, anybody working outdoors is at risk of heat stroke.