I have long reported EA has signals blocked sooner and longer than the WA, I have both in CT and WA in Tampa. I had EA in Fl and switched to WA when DISH changed the recommended ARC, because of exactly this. In the middle of the afternoon in Summer downpours either will go out, but WA not as long or as often.
In Ct it's an easy answer why my WA just about never has lost a signal from snow but it's a little more routine for the EA, it's the angle of the DISH. WA is closer to straight up and down, EA is angled upwards and catches the snow. Luckily most snow is the dryer type and does not block the signal. But if it stays on the DISH and the sun comes out, the moisture builds and then the signal may go out.
All that said however, if the OP has the signal go out everytime it rains something is wrong. My EA rarely goes out when it rains in CT (WA even less often) and when it does it may not even be raining, it's the dense storm head passing by. It's not unusual for it not to go out when the actual rain arrives, but only the couple of minutes as the Storm head approaches.
Also, I have never in something like 15 years had the signal go out simply because it was snowing no matter how hard or heavy, on either ARC, it's always the build up on the DISH.