The common weather of Sapa during the winter time is about 10 degree celsius (November to March), it would be wise to bring some good jackets with you. 

Footprint's experience that Sapa even had some snow during the winter time, but as you know the global climate is getting warmer so chances of snowing in Sapa would be very rare. In recent years, the coldest temperature is 3 degree celsius but this does not last long (often in about 2 - 3 days) then would pick up again.

If you are trekking to the remote villages, please note that the temperature in the village is always warmer than in Sapa, about 3 - 7 DC different.

See the best time to visit Sapa here: http://www.footprintsvietnam.com/FAQs/Sapa/Best-time-to-visit-Sapa.htm

See also other FAQs

What should I bring as a gift to the homestay family?

How does sleeping work in the homestays?

How do I prepare before going to the homestay?

What kind of food will we eat at the homestay?

What types of activities should we expect to be participating in at the homestay?

Are we sleeping with the family at the village in the same house? Do we eat with the locals at the homestay?

What do you mean by CBT homestay?

What kind of shoes should we use for trekking in Sapa?

How do you define: easy trekking, intermediate & hard trekking?

Is there anywhere in Sapa or Lao Cai, that we can get changed, have a shower, and leave luggage before our trekking?

Is your local guide waiting for us at the train station of Lao Cai?

How far is that from Lao Cai to Sapa and mean of transport?

Any other means of travel to Sapa except train?

Is there a day train to Lao Cai (Sapa)?

Is there a sleeper train to Sapa? What is it like?

Before our night train to Sapa, do you have a place where we can leave luggage?

When is the best time to visit Sapa?