An amber cold warning alert has been issued by the Met Office and the UK Health Security Agency.
The alert is a warning that the impact of cold weather is likely to be felt across the whole health service for an extended period of time and vulnerable people should take action to keep warm.
It remains in place until midday on Friday.
Cornwall is included in the alert, which also covers Devon, Somerset, Wiltshire, Dorset and Gloucestershire.
Professor Dominic Mellon, regional deputy director for the UK Health Security Agency (UKHSA) South West warned of the impact of cold weather on health.
He said: "It is important to check in on the wellbeing of those most vulnerable to the cold.
"Temperatures are expected to turn particularly cold overnight, as we would expect at this time of year.
"If you have a pre-existing medical condition or are over the age of 65 it is important to try and heat the rooms where you spend most of your time, such as your living room or bedroom, in the coming days."
The UK Health Security Agency has issued the following advice on how to keep warm:
- Check the weather forecast and the news
- Make sure you have sufficient food and medicine
- Take simple measures to reduce draughts at home
- Keep bedroom windows closed
- Wear multiple layers of thinner clothing
- If you're eligible, get vaccinated against flu and Coronavirus
- Get help if needed - call NHS 111 or 999 in an emergency