A rare cold weather alert has been issued by the UK Health Security Agency as temperatures are expected to plummet below freezing by the end of this week.

The level three warning, covering all of England, comes into force on Wednesday evening with the Met Office forecasting bitterly cold temperatures and the chance of wintry showers and some snow on higher ground.

Such a severe cold snap is being caused by an arctic maritime airmass, says the Met Office, which is pushing icy weather across the whole of the UK. This is expected to lead to lower than average daytime temperatures, overnight frosts and some chances of snow.

Met Office deputy chief meteorologist, Rebekah Sherwin, explained: "Temperatures will start to dip this week, with daytime temperatures struggling to get above freezing in many places from mid-week onwards. However, the cold air from the Arctic will also bring brighter conditions, with some dry, sunny spells in many areas, particularly away from the coast.

"Showers will turn more wintry as the week goes on with a risk of snow at times. A yellow National Severe Weather Warning for snow has been issued for Wednesday covering northern Scotland. We can expect to see some snow and wintry showers further south as the week progresses, particularly in coastal areas or over higher ground. There will be widespread frosts with temperatures falling to as low as -10°C overnight in isolated spots by the end of the week."

While it is not entirely clear how far into the weekend the cold snap could last, the cold weather alert which has been issued by health officials, is set to remain in place until Monday, December 12.

The warning, which focuses on how much of a risk such a significant drop in temperature can pose to the elderly or those with underlying health conditions, carries advice on how to see out the cold weather safely.

Dr Agostinho Sousa, consultant in Public Health Medicine at UKHSA, said: "Cold weather can have serious consequences for health, and older people and those with heart or lung conditions can be particularly at risk.

"If you have a pre-existing medical condition, you should heat your home to a temperature that is comfortable for you. In rooms you mostly use such as the living room or bedroom, try to heat them to at least 18°C if you can.

"Keep your bedroom windows closed at night. Wearing several layers of clothing will keep you warmer than one thicker layer."

This evening, Kent County Council urged people to keep an eye on each other. They said: "A severe weather alert has been forecast by the Met Office. We urge local communities to help look after vulnerable family, friends and neighbours by following basic common sense advice to keep them safe and well at home, and if needing to travel."