I don't want to drive a rental car up there and encounter snow. Anyone ever been up there first couple weeks in Feb? Is it passable everywhere?
I believe the roads (Hwy 9) is usually plowed and sanded, so driving to Zion is not a problem, unless it's during/right after a big storm. But many of the trails will be closed. That said, I went to Bryce/Zion in April one year and got snowed in at Bryce for 2 extra nights. Keep your eye on the weather forecast and adjust accordingly.
I agree with Sonya, "it depends". I was there in February already, no hiking this time. All the roads snowless, it was beautiful with the snow on the rocks. And nearly no people and you could drive into the valley.
I visited Zion a few years back around the middle of January. I didn't have any problem with driving/roads. I tried hiking on some of the trails, but encountered snow and ice covering the paths in many places, which made footing very slippery. I had to abandon trying to get to the three pools area. The park was deserted and I was able to get some great photos of the wildlife, especially some close up pics of mule deer that were by the main road to the lodge. Naturally, you won't be hiking the "Narrows". More than likely you will have the place practically to yourself; which is quite different from the summer months. Since there won't be any shuttle buses running, you will be able to drive 'deeper' into the park with your own car.
I don't know about February, but I was driving through the Bryce/Zion region last March and encountered a small snow storm there. Most of the roads remained open, but there was a lot of snow. I was happy that I was driving an SUV....
The obvious moral of the story is your mileage will vary. We and everyone else were ushered out of Zion late summer six or seven years ago because of flash flood concerns, and I will tell you, I've never seen rain like that as we headed back to St. George. We pulled over in Hurricane for a good 30 minutes to ride out one particular gully washer. February certainly is a beautiful time of year and any time the crowds are down is a winner.