It's pouring here today, which reminds me to tell you...
pick up a couple of cheap, washable throw rugs at Walmart or Target.
Then on rainy days (or especially snowy days) you can toss these out as extra protection by your main entrance.
Once the sun comes out - give them a good shake or a wash if necessary, roll them up and stick them back in the closet or basement until next time.
I like the rubber backed rugs for saftey and durability - just don't toss them in the dryer, either stick them out on the line or over a drying rack.