Ottawa Public Health has issued a frostbite advisory for the city in the overnight hours from Saturday until Tuesday.

The public health agency issues the advisory when the wind chill is expected to hit -25 and below.

Public health officials are advising parents to ensure children are dressed with warm layers and their skin is covered.

Here is everything you need to know to avoid, detect and treat frostbite, according to health officials:

Get to a warm area before frostbite sets in. If it is too cold outside, consider staying indoors.

Keep extra mittens and gloves in the car, house or backpack.

Wear larger mittens over your gloves.

Wear a scarf to protect the chin, lips and cheeks. They are all extremely susceptible to frostbite.

Wear two pairs of socks — wool if possible.

Keep feet warm and dry.

Do not drink alcohol, which narrows blood vessels and promotes frostbite plus hypothermia.

If you are wondering if you might have frostbite, there are four signs. Health officials call them the four "P's:"

Pink: reddish in colour (first sign).

Pain: becomes painful.

Patches: white, waxy-feeling patches show when skin is dying.

Pricklies: areas feel numb.

If you do notice you have frostbite, Ottawa Public Health advises you do the following:

Do not rub or massage affected areas. It may cause more damage.

Warm up the area slowly. Use a warm compress or your own body heat to re-warm the area but don't use a compress that is too hot. Underarms are a good place.

If toes or feet are frostbitten, try not to walk on them.

Seek immediate medical attention if you see white- or grey-coloured patches or if the area is numb.

Paramedics advise residents to seek immediate medical attention if you notice a severe frostbite. Temperatures below -40 C can cause frostbite within 10 minutes.