I opted for the latter and told the students to go outside for a few minutes to play. I figured they'd get cold and be happy to come back in. I was amazed at the fun they were having with barely any snow on the ground, so I decided to weave some math into the fun.
In groups students had to make the biggest snowball they could, and I said there would be prizes. They used rulers to scrape any snow they could off the ground and make it into a ball. This was a difficult task as it wasn't good packing snow.
Once everyone's fingers were frozen we came back inside with the snowballs. Students brainstormed all the ways we might determine which was the biggest snowball, and the problems with each method. Some wanted to weigh the snowballs, and we discussed how some might be more dense than others because of packing tightly. Other students wanted to measure the height and width of the snowballs, but I pointed out how some were irregularly shaped and not spheres.
Then we talked about volume and how that might be a good measure of the largest snowball. Again, the irregularly shaped balls and how this would not work. However, because I did not want to leave the class to go to the science storage room to get a scale, we decided to attempt to calculate the volume of the snowballs.
First we googled the formula for volume of a sphere and wrote it on the board. Some of the more advanced students examined the formula to determine what we would need to calculate the volume. We would have no accurate way of determining the radius of our snowballs, so we decided to estimate as best we could by measuring the height of each snowball (understanding that they were somewhat irregularly shaped) and using this as diameter.
Once we halved the diameter to arrive at the radius we worked our way through the formula together on the front whiteboard. Many students were not familiar with multiplying fractions, Pi or exponents, so they had a steep learning curve, but the stronger students helped walk us through the process.
We did this for the top three snowballs and came up with an approximate tie between two. By this time the snowballs were starting to melt so I let the students go back outside and throw their snowballs. This was their favourite part, of course!
As luck would have it, a couple of weeks later we had a large dump of snow on the last day of school before the winter break, so we had another big play outside in the snow. This time we skipped the math!