If you do end up putting it out in the snow, make sure to do it at night so as not to expose the quilt to UV light. And you probably want a drier snow (I guess that's maybe the idea behind it being the "first snow"), but I personally would be really reluctant to put a vintage quilt out in the snow, especially when it's a family heirloom.

For new quilts, I usually recommend that owners consider vacuuming the quilt more than washing it. You just put a nylon stocking over the hose & gently run it over the top of the quilt. It really does work! Here's a link to an article I read a while back about cleaning new & vintage quilts:
http://www.nationalquilterscircle.co...clean-a-quilt/

I would love to see a picture of the quilt, especially since we know the year it was given. It would be interesting to see the type of fabrics used. I have been volunteering sewing hanging sleeves on quilts at our local university museum. It is so much fun to see the fabrics and block designs used during different eras in history.

If you have a green lawn, lay a sheet out on the lawn, then the quilt, backside up, and let it sit either overnight or put out early in the morning when there is dew on the grass. Can cover the quilt with another sheet if you lay it out under trees or have lots of birds.

RetroClean. I am not in any way connected to the company. I used it on my great-grandmother's quilts which hadn't been cleaned for a good long time. The directions were easy to follow and the water with the RetroClean was used for more than one quilt. I used a large plastic bin and put it outside so the heat from the sun would do its magic.
Whatever you choose, good luck.
P.S. Snow will have particles of 'junk' in it from the environment. Depending on where you live it could leave residual
dirt that is worse than what's already in it.

I remember my Mom taking our wool coats and my Dad's wool suit outside, rubbing them in snow (I grew up in Saskatchewan and believe me, we had no shortage of snow) in the middle of winter--definitely not to first snow. No, I would not do it with a quilt as old as this one. If you have a museum near you, give them a call and ask to talk to someone in the preservation area.

How blessed you are to have found such a treasure. What about checking with a museum to see if they have any suggestions about how to clean it properly.

Be sure not to lift a wet quilt getting it out of the tub on its own without a sheet underneath to bear the weight!

How very lucky you are to have found such a treasure! If no one in the family wants to continue your legacy, please donate it to a museum where people can study it and where it will be taken care of in an appropriate manner.

What a wonderful find! how lucky for you

I vote for the snow. If you can find a time when the snow is still clean. If you've ever taken the wash off the line after it's been snowed on, you know how wonderful it smells. Just leaving it outside overnight when it's really cold helps, too.