#1 In inclement weather you can still get in a great practice by hitting on a racquetball court against the wall. This is also a great place to practice with beginners and/or little kids with less running around after errant balls. With the little ones, make it a "game" and make it fun!
#2 Here's a variation on hitting the wall which I learned from Oscar Wegner: take a piece of 4x4 plywood and lean it against a wall at an angle. Hit volleys against this slant board until you can do 100 on each side, then 100 on alternating sides. If your form is correct you will be able to do this with practice and without straining your arm. The more slanted the board the easier it is to volley. Start close to the board then work your way back. This drill will really help your form! My 6-year-old grandson loves to "play" this "game" with me.