UK Here. We have plenty of rain also and cold wet winters, not a drop inside any of my cameras after several years of usage.
Likely issues are as above either improperly secured SD card slot or another possible cause, improper fitment of the wires into the rear of the camera ie bad direction of cable feed eg. from above, (below very preferable with side feed as a fall back), not using grommets or putting huge / wide cuts in them, not forming drip loops behind the camera body when not fed from below, etc.