Let me share a couple of thoughts about what I do to help us practice fielding and throwing in general in cold and/or wet weather.
All you need is a big expanse of asphalt.
I buy those orange, dimpled, ATEC balls and use them for practicing throwing and fielding hops.
I buy low-bounce street hockey balls to practice fielding grounders. They simulate the action of a ball on a clay infield and force my guys to keep their gloves down.