Extreme weather continues to sweep across U.S.

LOS ANGELES, July 6 (Xinhua) -- The United States continues to experience extreme weather conditions as severe thunderstorms, critical fires and excessive heat waves sweep across the country.

Strong thunderstorms are expected across the western High Plains on Thursday with damaging wind gusts, large hail and a few tornadoes. This threat will extend into the Central and South Plains, coinciding with the potential of excessive rainfall, according to the U.S. National Weather Service (NWS).

Heat continues to build across the Pacific Northwest this week with temperatures approaching or exceeding triple digits at times away from the coastline.

On Thursday, heat advisories and excessive heat warnings are in effect for several spots across the country.

Dangerous heat will persist across the Southern United States from the desert of southern California to Louisiana and parts of Mississippi into the weekend and next week, according to NWS.

The United States has seen a noticeable spike in calls and hospital visits due to heat related illnesses during the middle and latter portions of June, especially in the southern regions, according to NWS.

The persistent heat wave has increased risks for wildfires. A Red Flag Warning for wildfire has been issued for much of Northern Arizona for both Thursday and Friday due to strong winds and very dry conditions.

Red Flag Warning is the highest level of weather-related fire warning. The warning will normally be issued for severe fire weather events less than 12 hours in the future.

Strong winds and low relative humidity are predicted for a large swath of Arizona. Campfire restrictions remain in place throughout the region on nearly all public lands, according to NWS.

Meanwhile, very hot temperatures are set to remain in place for parts of the region. An excessive heat warning has been issued for the Grand Canyon through the weekend.

Extreme weather events, which claim more lives than hurricanes and tornadoes, will likely increase in the future, experts said.

Each year in the United States, thunderstorms produce 20 to 25 million lightning flashes that strike the ground, killing an average of over 20 people and injuring hundreds more, often in devastating and permanent ways, according to NWS.

Older people and those with diabetes, obesity, heart disease and other serious health conditions are most at risk for severe weather conditions.