Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services if cold exposure is followed by confusion, slurred speech, poor coordination, very slow or shallow breathing, or difficulty staying awake.
These can be signs of hypothermia.
A measured body temperature below 35°C or 95°F is also an emergency.
Chest pain, fainting, severe breathing difficulty, or new confusion need emergency care instead.
And for anyone, someone who:
Seek same-day medical advice if cold intolerance has suddenly become severe or occurs with marked weakness, worsening breathlessness, a racing heartbeat, or significant dizziness.
Book a routine appointment if the symptom lasts for several weeks, keeps getting worse, or affects sleep, work, or usual activities.
It is also worth arranging an appointment if you have unexplained weight change, persistent tiredness, constipation, heavy periods, unusual bleeding, hair or skin changes, or repeated painful colour changes in your fingers or toes.
The article also says
While waiting for help, move into shelter if it is safe, remove wet clothing, and use dry blankets.
Avoid placing very hot objects directly against numb skin.
Every sign above is quoted from the sofidex article on Cold intolerance. If you are not sure, err upward — it is always reasonable to be checked.