So the MR42E is not outdoor rated, so you would have to have it protected some how with a NEMA enclouser of some kind. If you had it inside, and the antenna outside, in theory that would work. However the MR42E supported antenna options are also not technically 'outdoor' rated, the way the MR74 ones are.
So you might eventually run into water damage issues getting inside the housing etc.
However, here are some options for you that could get it 'weather proof'
http://www.ventevinfra.com/meraki-mr42/http://shop.acceltex.com/index.php?cPath=30Might require some customization (drilling holes, weather proofing yourself) etc.