A European heatwave, which has claimed the lives of an estimated 40 people over last two weeks, may be temporarily interrupted over the next few days.
The storms will come too late to save some drought-stricken crops
Forecasters are predicting cooler weather with thunder storms before the heat returns again at the weekend.
The high temperatures - above 35C (95F) in some places - have been accompanied by increased pollution and drought.
In many countries, farmers are worried about the possibility of crop failures and loss of income.
In the town of Turin, northern Italy, where the temperatures hit 40C (104F) the heat has been blamed for the death of a woman of 89 and a man of 87.
In Barcelona, north-east Spain, the death of a woman of 83 was registered as the ninth fatality in the country due to the scorching weather.
In France, the heat has brought back memories of the summer of 2003, when about 15,000 people died, most of them elderly, sparking criticism of the country's social services.
French farmers have called for help, fearing that damaged crops will lead to financial losses similar to the situation three years ago.
"[The year] 2003 remains a black year for French farmers and unfortunately has become a reference point for the agricultural world," the main French farmers' union said, quoted by Reuters news agency.
According to reports in the Polish media, the capital Warsaw has experienced the hottest July since records began more than 200 years ago.
Polish firefighters are on high alert to tackle forest fires caused by the drought. There have been more than 8,000 fires in recent days.
High water temperatures have also disrupted electricity production at nuclear power stations in France and Spain, which use water as a cooling agent.
Electricity supplies in the Czech Republic were back to normal on Wednesday after widespread blackouts due to overload the day before.