BRITAIN is to be hit by an unseasonal Spring heatwave - just as millions go into coronavirus lockdown.

Forecasters say a 500 mile-wide 'Portuguese pulse' of warm air will blow in 15C highs across the UK for up to 10 days.

A weather map shows air blowing from Portugal to Britain, with highs climbing to 15C – 4C above average - by Wednesday.

The Met Office predicts mostly dry conditions for 10 days - meaning the isolated can at least enjoy some quality garden time.

Yesterday it was revealed letters have been sent to around 1.5m of Britain's most vulnerableby the government - telling them to stay at home to save their lives.

Housing Secretary Robert Jenrick confirmed thousands at risk of not recovering from coronavirus have officially been told to stay in for 12 weeks.

It comes as 5,018 people are now infected in the UK, with 233 deaths reported yesterday.

Around 1.5 million personally addressed letters have been sent out to those judged most likely to die from the killer virus, The Times reports.

They have been warned they should cut themselves off to protect themselves from the deadly bug.

The letters tell those at risk to avoid anyone, including people in their own home, with symptoms.

They mustn't go out for shopping, leisure or travel and supplies need to be left at their front doors for their own protection.

Robert Jenrick said the government will explore “other options” if health advice is continually ignored by the public.

The warning from the Communities Secretary came after reports of crowds flocking to seaside resorts this weekend.

While this morning Boris Johnson wrote to Brits urging them to stay at home on Mother’s Day and added that we need “to act together” to avoid the same fate as Italy.