Red alerts for extreme heat are in place in most of Italy's main cities as a heatwave intensifies in Europe. Temperatures are expected to peak on Wednesday, with 23 cities on high alert – from Trieste in the north-east to Messina in the south-west. Wildfires are also raging across the continent, including in Greece and the Swiss Alps.<br />'' <br />''Millions of people in the northern hemisphere are being affected by scorching temperatures. It is being caused by a high-pressure system bringing warmer, tropical air, south of a jet stream currently stuck over central Europe. Parts of the Italian islands of Sardinia and Sicily will be the hottest again, with highs of around 46C or 47C.<br />'' <br />''<span style="color: #222222;">The Italian health ministry has asked emergency rooms across the country to activate so-called heat codes, assigning a separate group of medical staff to treat people who come in with symptoms caused by the heat.</span><br />