As Trump took the stage just after 17:00 EDT (22:00 GMT) at a mega-church in Phoenix, the temperature was 111F (44C).
It was his first rally since his criminal conviction in a New York hush-money case, which found him guilty of falsifying business records in relation to a payment to adult-film actress Stormy Daniels.
The former president spoke for about 90 minutes before departing for a fundraiser in San Francisco.
As well as railing against his conviction, he said he would reverse President Joe Biden’s new executive order aimed at curbing migrant arrivals at the US-Mexico border.
The intense heat has placed more than 30 million people across the south-west region under alerts for dangerously hot temperatures, with officials asking residents to take precautions.
Heat-related illness and even death are becoming more common in Phoenix and the American south-west.
Best in Moderation
Article URL : https://www.bbc.com/news/articles/crgge744qpeo