The Met Office has issued a cold weather alert this week starting on Wednesday 7 December, with temperatures expected to drop well below freezing in some areas across the country.

The UK Health Security Agency (UKHSA) has encouraged people to stay warm and look out for those most at risk from the effects of winter weather. "Cold weather can have serious consequences for health, and older people and those with heart or lung conditions can be particularly at risk," says Dr Agostinho Sousa, consultant in Public Health Medicine at UKHSA.

With that in mind, many of us will be wondering whether we should leave the heating on overnight during colder conditions. Here's what you need to know.

Read more: How to stop arguing about the heating and keep your home warm this winter

Should you leave the heating on overnight when the temperature drops?

When deciding whether to leave the heating on at night time, it's useful to know what temperature experts advise your home should be in winter.

The Energy Saving Trust states the thermostat in your home should be set to the lowest comfortable temperature (usually between 18C and 21C), while an official report also outlines 18C as the recommended minimum. The vulnerable may wish to heat it slightly higher, and healthy people may wish to heat it slightly less.

And this is similar for overnight.

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"It is widely accepted by sleep experts that the ideal temperature for sleep is approximately 18.3C, although we also know this varies slightly person to person," says Nuffield Health physiology national lead, Louise Wright.

"For those over 65 or with pre-existing medical conditions, a systematic review by Public Health England in 2014 stated that maintaining the 18C threshold overnight may be beneficial to protect health, alongside the use of sufficient bedding, clothing and thermal blankets or heating aids as appropriate."

For babies, The Lullably Trust advises that a room temperature of 16-20C – with light bedding or a lightweight, well-fitting baby sleep bag – is comfortable and safe overnight.

How does the temperature at night affect your health?

Being too hot, or too cold, will disrupt your body's ability to get a good night's sleep and keep you healthy.

"A person's core body temperature is regulated by the circadian rhythm," explains Wright. "This means, like our hormones, it rises and falls over a 24 hour period. At night the core body temperature should drop slightly, coinciding with the release of the sleep hormone melatonin, and this signals that the body is preparing and ready for sleep.

"The body starts to cool itself through the process of vasodilation, allowing the blood flow to move away from the core towards the extremities (and this is why you sometimes experience hot feet and hands at night!)."

Read more: How much sleep you need at different ages, from childhood to the later years

But, Wright adds, "If where you are sleeping is too warm however, this can interfere with your body’s thermoregulation and therefore cause discomfort and restlessness, as well as a decreased amount of time spent in the restorative stage of sleep."

Overall, it's generally thought to be better to be too cold, than too hot, while trying to sleep, but as you obviously don't want to suffer the implications of shivering through the night, consider whether it's important for you individually to keep your bedroom heated to the 18C minimum, or whether you can stay warm in other ways.

Products to help you stay warm

Wearable Hot Water Bottle | £25 from Amazon

Teddy Bear Cream Long Hot Water Bottle | £14 from Dunelm

Fogarty Superfull 10.5 Tog Duvet | £35 from Dunelm

Silentnight Comfort Control Electric Blanket | £35 from Amazon

Grey Oodie | £64 (Was £89) from Oodie

Heatgen Plus™ Fleece Thermal Leggings | £16 from Marks & Spencer

Heatgen Plus™ Fleece Thermal Turtle Neck Top | £16 from Marks & Spencer

Thermal Medium Warmth Long Sleeve Vest | £18 from Marks & Spencer

Light Warmth Thermal Long Johns (2 Pack) | £25 from Marks & Spencer

Heated Vest | £52.99 from Amazon

Watch: Martin Lewis shares tips on how to stay warm cheaply