Editor’s Note: A version of this article originally appeared in the weekly weather newsletter, the CNN Weather Brief, which is released every Monday. You can sign up here to receive them every week and during significant storms.
Intense summer heat will build as the week rolls on, peaking with potentially deadly heat in the drought-stricken West this Friday.
Temperatures will rise above 100 degrees, reaching or breaking records in many areas. Meteorologists like Chris Kuhlman, from the National Weather Service (NWS) office in Phoenix, recommend people stay indoors.
“It’s going to be hotter than what we’ve seen any time this year so far,” Kuhlman told CNN Weather. “We’re tacking on another probably 10 degrees, so it’s definitely going to be hot.”
Heat waves are the deadliest type of weather disaster in the US. They account for nearly 150 fatalities per year, more than hurricanes and tornadoes combined.
“This heat will impact everyone, not just those sensitive to heat risk,” the National Weather Service in Sacramento emphasized in a tweet.
In California, heat waves are becoming such an issue new legislation was introduced in California earlier this year, in hopes of reducing heat-related deaths by ranking heat waves similarly to hurricanes by using categories and names.
The NWS is also considering categorizing heat waves and is in the process of using an experimental product to forecast the effect heat will have on people. This week, heat will push the top of the scale.
The heat will be so intense, it will reach the highest two risk categories on the National Weather Service’s experimental heat risk tool.
Most of the Southwest will be blanketed with a Level 1 or 2 heat risk all week. By Friday, a Level 3 will cover most of Central California, including Sacramento and across the deserts in California, Nevada and Arizona.
In Sacramento, California, where temperatures will reach triple digits Friday, the National Weather Service office cautioned, “heat like this only happens a few times each year.”
In places like Las Vegas and Phoenix, conditions will reach Level 4, considered a ‘very high risk’ for the entire population due to long-duration heat, with little to no relief overnight, the NWS pointed out.
“Emergency room visits due to heat-related illness are four times higher on ‘high’ and six times higher on ‘very high’ heat risk days versus ‘low,’ ” the NWS in Phoenix noted.
Here is why nighttime extreme hot temperatures can be deadly
The reason behind the extremely high temperatures is an area of high pressure creating a clear lid over the Western US. The lid will trap any escaping radiation and send it back to the ground, while the sun’s rays continue to penetrate through.
It’s called a heat dome.
“You can also call that a heat dome: a high, an area, an air mass that is hot and got a lot of sunshine, and it’s just going to get basically hotter through the time here,” Bryan Jackson of the Weather Prediction Center (WPC) told CNN Weather.
The WPC emphasized the heat dome will combine with dry soil to allow temperatures to rise to record levels over parts of Texas.
West Texas will see the first round of extreme heat early in the week, followed by a more widespread heatwave at the end of the week and into the weekend.
“In the summertime, we do have temperatures that are exceeding 100 degrees, but this is a little early for us to have these temperatures this hot,” Jim Wingenroth with the NWS in San Angelo observed. “So, it’s well above normal temperatures for early June.”
The temperatures in Texas and across the Southwest are being magnified because of arid soil.
When there is no moisture in the soil or in plants, there is no evaporation or evapotranspiration, both of which are cooling processes that add moisture into the air and stabilize the air temperature.
“Basically, the drier the air, the easier it is to get to a high temperature,” Jackson explained. “When there’s more humidity, the temperature can be suppressed.”
The temperature may ease slightly after its peak on Friday, but the six to 10-day outlook from the CPC shows a high percentage of above-average temperatures continuing through the weekend.