As noted in your previous thread, you need more antenna plus a preamp.
http://forum.tvfool.com/showthread.p...9560#post49560
As far as the rain vs dry goes, the water or lack thereof changes both the reflective and the absorptive nature of the terrain and foliage over which the signals must diffract or reflect. When you're barely hanging onto the reception by the edge of your fingernails, figuratively, it takes very little disruption of the propagation path to push your reception over the edge of the digital cliff.