Met Office has issued an urgent warning ahead of a new heatwave set to hit British shores– and has revealed when it will end.Temperatures are set to climb to around 35C in certain parts of the country this week, with extreme heat warnings placed across southern England, Wales and the Midlands from Thursday (August 11).Drought warnings are also in place for certain parts of the country, while Thames Water is expected to announce a hosepipe ban in the coming days.READ MORE: Double heatwave health alert issued for people with heart, lung and asthma conditionsBut experts from the Met Office are also issuing a warning about rising temperatures at night, too – just a few weeks after all previous temperature records were broken by a 40C heatwave last month.Met Office deputy chief meteorologist Dan Rudman said: “Thanks to persistent high pressure over the UK, temperatures will be rising day-on-day through this week and an Extreme heat warning has been issued.“Temperatures are expected to peak at 35C on Friday and Saturday, or even an isolated 36C on Saturday.“Elsewhere will see temperatures widely into the high 20s and low 30s.“Coupled with the high daytime temperatures there will be some warm nights, with temperatures expected not to drop below the low 20s for some areas in the south.“Some change to more unsettled conditions is then signalled but, as is often the case during the summer, details a week or more in advance of showers and rain are highly uncertain.”A Level 3 Heat Health Alert has also been issued by the UK Health Security Agency, which comes into force from tomorrow.The agency is urging everyone to check on older people, as well as young children, and make sure they are as cool as possible and that they are also