A spokeswoman of the Governor's Office of Emergency Services said they were working to confirm that the recent deaths of 71 people were due to the record-breaking heat.
"These are deaths that are believed to be due to the heat or related to the heat wave," spokeswoman Tina Walker told AFP.
"However, until toxicology records and autopsies are performed, it won't be certain that that was the cause," she said.
Most of the dead were elderly people living in the hot central valley between San Francisco and Los Angeles.
Europe continues to swelter
In Europe, a deadly heatwave continues to sweep across a swathe of countries, and has lead to forest fires, forced water restrictions and damaging farmland across the continent.
Now firmly in its second week the heatwave has brought temperatures of more than 30 degrees Celsius to most of Europe with hotspots in France, Germany, Spain and northeast Italy.
More than 50 people are estimated to have been killed by the heat.
But so far there's been no repetition of the massive loss of life in the heatwave of 2003 when 15 thousand died in France alone.
Forecasters predict storms and wet weather will spread east across western Europe towards the end of the week, dousing Britain, France and Germany.
The change in weather is expected to bring relief to the millions suffering the high humidity, sticky nights and blazing sunshine.
Preventing heat-related deaths
Greater awareness, slightly lower temperatures and preventative action by European governments to protect the elderly are believed to have helped limit the number of deaths.
Nevertheless, in Italy the heat killed a man of 87 and a woman of 89 in the northern city of Turin during the last night, the Italian ANSA news agency reported today.
And in Spain, the death of a woman of 83 in Barcelona in northeast Spain brought the toll in that country to nine.
Water concerns
In France on Wednesday, the mercury climbed to 38 degree Celsius in the south of the country while Parisians faced a sticky 36 degree Celsius.
French Environment Minister Nelly Olin warned that groundwater levels in the Paris region were at their lowest level in 20 years and said that water restrictions were in place for nearly half of the country.
"It needs to rain without storms. That would be the ideal situation but I don't think we're there yet today," she told French television channel France 2.
The temperature in the German capital was set to hit 36 degrees in the next few days before storms on Saturday.
The level of the river Elbe which crosses Germany's main port Hamburg has dropped below 90 centimetres upstream at Dresden near the Czech border, making navigation almost impossible. Normally the level is some 2.2 metres.
Fire threat
In Poland, firefighters were on maximum alert to tackle forest fires caused by the drought. Over 8,000 fires have broken out in recent days and access has been banned to most forests.
According to the Gazeta Wyborcza newspaper, Warsaw has seen the hottest month of July since temperatures began to be recorded 227 years ago.
The average temperature in the Polish capital this month was 23.2 degC, five degrees higher than the norm.
In Denmark, undergoing one of the hottest summers on record, many local authorities have banned open air fires except at fixed barbecue sites.
Electricity supplies in the Czech Republic were back to normal Wednesday after widespread blackouts caused by overload the day before.