If you live in an area with snow, have you ever tried water color painting with snow? We grabbed a large sensory bucket, a few shovels full of snow and brought it in to the classroom. In the past we have used tempera paints with added water, to water it down and we have used just regular water color paint sets. Both work just fine in creating painted snow art. You could even give each child their own plate of snow to paint as an individual rather than a group activity.
After we got done painting the snow the kids wanted new snow to just play in. We ended up driving hot wheels cars through it, and our play dinosaurs and animals. It was cold and we got wet but the kids were happy and wanted a second tub, but we ran out of time. After reflecting on the activity later we realized it would have been a good day to try out making hot chocolate with the kids.
For sensory tubs we use some restaraunt dish tubs we were given. WE LOVE THESE, they are super sturdy and hold up better than the tubs you find sold and labeled as "sensory tubs". Here's a link to the closest thing we have found to the restaurant tubs we have. When working with little kids "Sturdy" is necessary!