BANGKOK (AP) — Extreme heat has sent temperatures soaring in Thailand as authorities warned people to stay indoors.

The Meteorological Department’s forecast on Saturday said the highest temperature in the next 24 hours could reach 43 degrees Celsius (107 degrees Fahrenheit) in country’s north and could hit 40 C (104 F) in the capital, Bangkok. The highest temperature on Saturday was in the northern province of Phetchabun at 42.5 C (109 F).

“Even if I turn the air conditioning to 20 degrees, I still sweat,” said 37-year-old Supichaya Jittaleela, who attended an outdoor political rally despite the heat.

People should be wary of extremely high temperatures as well as sudden summer storms until at least next week, the weather department said. A police officer directing traffic in Samut Prakarn, a province just south of Bangkok, collapsed and died of heart stroke, media reported this week.

Saturday’s highest heat index — which measures what the temperature feels like due to humidity — was forecast to be 53.8 C (129 F) in the eastern province of Chonburi. On Sunday, the southern resort island of Phuket could feel hotter than 54 C.

The heat was a problem for the 2,000 or so people at the political rally in Bangkok. Even though the shade from a shopping mall shielded them from the direct glare of the sun, many could be seen trying to cool down, with battery-driven and old-fashioned hand fans.

“It’s hot, much hotter. That’s why I have my fan with me,” said 63-year-old Rungtip Sangvittayothai. Thailand holds a general election next month.