Your doorbell is probably just a low-voltage one, so there's a transformer somewhere on that circuit. On newer houses, the transformer tends to be on or near the electrical switchboard, but in older places can "piggy back" on the back of an outlet or switch box that's exposed, like in a furnace room or unfinished basement....so it should be a long way from the potential ingress of moisture, besides, the low-voltage side of the transformer getting shorted out by moisture is not going to trip a breaker, in fact unless it's a GFCI, breakers take a lot of moisture to trip since rainwater's not a great conductor. So the issue is probably not your doorbell.

You have a serious problem that needs action, immediately, from a professional or professionals, if necessary. In fact, you have two problems - one, ingress of moisture, never a good thing, and in quantities sufficient to cause electrical problems. This is potentially very dangers, for another thing. I presume you mean you replaced the circuit breaker, which just shows the first one was doing its job, however, repeated tripping wears a breaker out (they all should be replaced after some period of service anyway) - you have already concluded there's a moisture problem which, as you've indicated, needs to dry out before things work again.

When you say lights at top and bottom of steps, do you mean outdoor lights? If they are, first thing to do is check if the fixtures themselves are full of water, you'd be surprised how often this happens - when you say it happens when it's raining hard, that suggests either a driving rain or a situation where water builds up more in some places than others.

So, if those lights are outdoors, inspect them and the seals and connections for leaks - six years is enough for seals and gaskets to fail, or the body of the light may be cracked.

The other possibility is a roof leak where your pool table light is, with water entering the wiring round there. If you haven't observed water round it then you're probably ok but next time it rains heavily, you could go up into the ceiling space with a good flashlight and see if you can see any problems.

If there are outdoor switches for those lights or a motion sensor or photo cell, these are all potential spots. If the lights are on poles or something or there's some underground wiring, these could flood too.

Of course make sure the power's off when you're checking these things because, apart from the usual dangers, there's bound to be a lot of water inside whichever part the culprit is - when you find it, it'll probably be very obvious.

Thanks for responding. Two things: the lights at the top and bottom of the steps are indoors on the steps heading down to the finished basement. The pool table is also in the finished basement. I can find no evidence of water anywhere around the perimeter of the house or the lights.

When I came home yesterday, I could tell the doorbell was on because it lights up. It wasn't until I turned on the lights for the finished basement that the switch tripped.

Well then, there's a clue. How are your fault-finding skills? Before you do anything, make sure you're working in a safe manner.

As a shortcut, you could try removing first one bulb from the two fixtures, then the other, Theoretically this will make one then the other open circuit, which may help solve things. Check connections on switch, and fixtures - replace if there's any doubt.

If you're sure about the rain aspect, you must have a leak. Where is the switchboard situated? How can the wiring for just that circuit be exposed to water? Check the neutral connections especially are tight, I've heard that can cause problems.

The recent rains seem to caused a similar problem in our house with the circuit for the lights upstairs blowing (upstairs plug sockets are all ok). I mention it in case it's connected but I was using the upstairs electric shower when the fuse box tripped. In addition, for the very first time, the driving rain penetrated the house finding gaps between lead flashing.

I've left the house to dry out a bit (a week) and tried the circuit again but it tripped after just a few minutes.

Should I leave the house to dry out some more before trying again or just call in an electrician now?

Sounds to me like someone tapped into the circuit to feed an outside receptacle or light.