More than 20 locations across the US were expected to either break or tie previous high temperature records on Sunday as the south of the country bakes in a heatwave. The National Weather Service had numerous excessive heat warnings in place across a 2,000 mile swath stretching from southern California through to Mobile Bay in Alabama. Potentially record-breaking temperatures are expected in southern California, Arizona, New Mexico and west Texas. Many of the impacted areas are also experiencing issues with surging coronavirus cases, and some experts and officials are anxious heat could increase infections if people shelter indoors, or in areas with less ventilation. Lara Pagano, a meteorologist at the Weather Prediction Centre, said there are 23 locations that they expect there to be “records tied or broken today”. The heatwave, which started on Saturday, is expected to peak in most places on Sunday but go on in Texas until Tuesday. In Phoenix, Arizona, records are predicted to reach 116F (46.6C) – which would break the previous record of 115F set in 2009. In California, Palm Springs is expected to reach 119F , nearing a record set in 1985 of 120F. In Texas, temperatures are expected to exceed 100F in San Antonio and Dallas. Pagano said the heatwave is being caused by high pressure over the area that is being exacerbated by unusually low monsoonal moisture. “Typically this time of year we tend to see more monsoonal moisture moving into the south-west so that can help temper some of the higher temperatures … It’s been delayed.” Residents of affected areas are advised to stay indoors if possible, but if not to stay hydrated. Heat advisories are also in place in the north-east in Boston and Providence where heat indexes of up to 96F (35C) are predicted. In Miami, Florida, Brian McNoldy, a senior research associate at the University of Miami’s Rosenstiel School pointed out that on Saturday the city had seen 20 consecutive days with a heat index of 103F (39.4C) or higher. “This seems extremely rare,” he tweeted. “Fits in with hottest year on record so far.”