New Delhi, Aug. 2 -- A powerful heat wave gripped large parts of the western United States on Saturday, pushing temperatures close to record highs, worsening wildfire risks and prompting authorities to urge people to stay indoors and hydrated.

According to the Associated Press (AP), a ridge of high pressure -- commonly known as a heat dome -- is trapping hot air over states from Arizona to Montana. While forecasters expect the heat wave to be relatively short-lived, dangerous temperatures and dry conditions have triggered warnings across the region.

Las Vegas recorded 115 degrees Fahrenheit (46.1degC) by late afternoon, the city's hottest temperature of the year and just one degree below its daily record. Phoenix was forecast to reach 1...