tobeamouse4,
Here's a link to 7 or so years of temps and rainfall.
http://www.srh.noaa.gov/mlb/mlbclimat.html
In 2005, the only year in the last several we didn't go this week, it was cooler than average with one day only getting a high in the 50s. This is very unusual. I can't remember an early March trip when we didn't get a couple of highs in the 80s, low to upper 70s is practically a given. As for rain, March is one of the three lowest months for rain. We've probably had 50 + park days in this timeframe over the years and we've had one day when it rained all day but other than that, a quick spritz and back to sun is the worst. We don't even think about the weather.
Crowds, I'd call 'Moderate'. Get to the parks early, use FP and you'll have a lot of fun before the crowds become an issue, usually around 1 pm or so. At that point we hop to Epcot and finish the day there as we usually stay at an Epcot resort, Epcot swallows crowds and rarely seems crowded to us and there's a lot of restaurant/pub selections there. Enjoy, and maybe our paths will cross.
Bill From PA