Lampang province became the hottest place in the country says after the official start of summer.
The Meteorological Department reported 40C in Thoen district of the northern province on Saturday, one degree higher than Lamphun and Phetchabun.
In Bangkok, Don Muang was the hottest district as temperatures rose to 36C.
Thailand officially began summer on Wednesday and several provinces have been battered by summer storms.
The weather agency's warning on Sunday said gusty winds and heavy rain were expected - mostly in northern and northeast provinces - for the next two days. Bangkok would be impacted by turbulent weather conditions, it added.
Nong Bua Daeng district in Chaiyaphum province was one of the places damaged by the storm.
Sawangkunnatum Foundation, a rescue volunteer group, said downpours and strong winds pounded the district on Saturday, damaging several houses, cars and a field hospital.