Will I need more than a light fleece jacket in Sapa? Am I right in thinking weather will be between 50 (night) and 70 degrees (day)?
What about Halong Bay? I am thinking maybe 70s during the day and 60s at night?
Thanks for any help!

You will need a fleece Jacket + a light sweater. it's not cold in November yet, but at night time in sapa it may get colder than normal. Though it depends on where you are from to say "cold".

Halong Bay is the same.

You will also need a rain jacket. I certainly did when we were there at that time of year.

the last time we were in hanoi in nov it was very warm...

I agree that Hanoi will still be warm in November. My husband and I did both Sapa and Halong Bay at that time and as I recall we took sweaters but didn't use them much. I suggest not packing either and if you need it--just buy one in the market...they are super cheap in Vietnam. Also leave your rain jacket home. They are too hot and you will sweat like crazy. I carry an umbrella and if it really pours, I always have a very cheap (less than $1) plastic raincoat in my backpack. These are the "use once and toss" type of raincoats. They weight 2-3 oz and work great if you need one.

By the way, I am back in Hanoi --teaching for the semester. Gad, I forgot how hot and humid it is here. I am looking forward to the "cooler" months of November and December.

Thanks. We'll probably pack a cheap raincoat and light fleece and buy a sweater if it is really cold. We live in the Seattle area and it is hard to imagine hot weather and not needing warm clothes.