A heatwave has been declared in multiple parts of England, while amber heat health alerts are in force across the country.Temperatures are forecast to soar to 35C on Monday and Tuesday for some parts of the UK in what is expected to be the hottest day of the year so far.The health warnings mean there is likely to be a “significant” impact on health and social services, and a rise in deaths, with alerts in place until 5pm on 27 May.A Met Office spokesperson said: “We rarely see temperatures above 35C, even in the summer months, so to see temperatures getting close to 35 in May is, as I say, pretty historic.”Temperatures will reach the mid-thirties on Monday (Met Office)Bank holiday Monday will bring scorching conditions for much of the country, with the possibility that temperature records for May could be broken. Parts of northern England and Wales are forecast to experience weather around 30C, while 35C is forecast in the southeast.Met Office forecaster Tom Morgan said: “We will see much higher temperatures compared to over the weekend...Parts of the Midlands, the east of England, and particularly the southeast will probably see temperatures nudging towards the mid-30s. It is likely to be record-breaking.”Temperatures in London are expected to rise to 35C, which would mark the hottest day of the year so far and the hottest May day on record.A heatwave has been declared in eight locations in southeast England, which have now met the threshold of 27C for three consecutive days of hot weather.On Sunday, temperatures reached 32.3C at Kew Gardens, in southwest London, while parts of southeast England exceeded 30C.Record-breaking temperatures are also forecast for Tuesday (Met Office)The Met Office has forecast similar conditions for Tuesday, with 35C weather expected in London again.Overnight and into Tuesday, temperatures in the south of England may not fall below 19C. The Met Office said the heat could spark heavy showers and thunderstorms by the afternoon in some areas, including Wales.“In the south, temperatures once again will be in the low-to-mid thirties for some, particularly across the Midlands, central southern England, and in the southeast,” Mr Morgan said.