My incredibly boss asked me if I felt comfortable going to work today because she had to work from home! The decision was on me so I went and she did pay me for yesterday and today the 8 hours eventogh I went late today! I love my charge and love the family,

I agree with PP. I live in an area that very rarely sees snow or ice. I don't have a snow sat policy in my contract. We were snowed/iced in for 2 days. I've worked for my family for 7 months. I've been happy and have never missed a day. I am flexible with all come in early/stay late requests. I go way, way above and beyond what is outlined in our contract because they always treated me well.
I was told they would not pay me for 2 snow days, despite the fact that the local and state government was completely shut down.
The days of me being flexible and going above and beyond are GONE. I will never do them another favor again.
Pay for the damn snow day. A little goodwill goes a long, long way.

Nanny here: I know this depends on the person, but I'm more inclined to be reliable and hard working if I'm with a family that appreciates that and is willing to work with me. As in, if I truly couldn't come in and they still paid me, I would be that much more drivin to make them feel like I'm worth that. I've worked for them for over a year and went home early once (I was very sick with a fever) an missed a few hours one morning due to snow. I was still paid for both of these instances and in return I have tried my best to always show up and do the best possible job I can.

Obviously some people would take advantage but just some foo for thought

MB here. We agreed with our nanny upfront on an outside agency to determine what is a snow day and what isnt (we use the agency where we work, but doesn't have to be that.)
Then if it's a snowday for them, it's a snow day for her and it's paid. Otherwise, she has to come to work. She has complained at least once when schools were closed and the agency we use was open, but she came it all worked out.

The real lesson is that this is one of the many things that it's helpful to spell out 100% clearly in your contract. And what you want depends on what your career needs are. For example, if you get lots of snow days (teacher) you might be more flexible. If you are an ER doc and have to go in no matter what, you probably wouldn't be and then you need to pay enough to ensure nanny can say, own a four wheel drive.

If you haven't done that you should agree on a policy with your nanny that you both think is fair and works for you. Ignore the people here reflexively whining one way or the other - the only people who care if it's fair at the end of the day are your family and your nanny.

"...even though I think the roads were eventually okay" -- are you crazy? way to be concerned about your nanny's safety.

As a nanny I don't get paid for snow days. I used my banked hrs. I only get paid for 45 hrs per week anything extra I bank and use on snow days or days when I work less. Works for us.

Also, if you do hourly pay, how do you handle holidays and vacation?

OP here. yes, i guess that's what it is. Doesn't seem like the best arrangement - i mean, yes, i do get paid if i don't come in on a snow day, even if perhaps i could make it (of course, i'm expected to telework), but i never get overtime, and i work lots of late hours.
what is the best way to do this (beyond the question of snow days?)? i want to be fair (to both of us) and legal.

MB here, I do not get paid on snow days by my job. I can take the day unpaid or take a PTO day. Nanny called out yesterday (totally reasonable) and today (questionable). I am at work today. My husband is staying home. I am not inclined to pay the nanny for these days. It is not in our contract and I don't think it should be assumed that she is paid when many people (myself included) are not. FWIW we have never asked her to come in early and have never, not once, been late at the end of her day. We do, however, often let her go early. I am fine that she called out if she felt like she was unable to come to work, but not so fine with paying her for it.

Nannies are not salaried. What OP is offering is *guaranteed pay*.

If nanny works beyond her regular hours, you pay her extra; right? And if she works less (if you let her go half an hour early one day, for example) she still gets paid for a full day; right?

That is not salaried. It's guaranteed pay.