Why does all your lights in your living room go out every time it rains?

You have a serious electrical problem in your living room. Chances are your roof is leaking into an electrical box shorting something out. Call a roofer and an electrician. I wouldn't recommend trying to DIY here, as there is something wrong that could kill you. Electricity can conduct through wet insulation from whatever is shorting, so you can get zapped poking around even if you don't enter any electrical boxes.

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If the lights go out suddenly (as opposed to flickering) it may be due to a ground-fault circuit interrupter. This can be triggered by moisture entering an outlet or appliance anywhere on the same circuit. Make sure that outdoor outlets are closed against moisture when not in use.