There are many people here who can help you solve the problem. We all need more information than what you have given.
Is it a gas or gas/oil mix mower? Do you add oil to the fuel or do you check oil with a plug or dipstick? Does it have the extra "dead man" safety handle? I would assume that a mower with a deadman lever will have electronic ignition.
Being rained on does not kill mowers. The chances of it being too wet to start is not likely.
Engines need 2 basic things - fuel and spark. To test for spark: Remove the plug from the block. Install the plug wire. Hold the tip of the plug against the block where you can see the gap in the spark plug. Have someone pull the cord. You should see a bright blue spark as the engine is spun. If you see no spark, first try a new plug. If you still see no spark, it is time to pull the flywheel. First thing to check is gap at magneto. Reassemble checking the condition of the woodruff key. Retry.
Failure to start is more liable to be moisture in fuel related. It sounds as if you should go to the library to get a repair book or find a friendly old duffer who could help you.
I just looked in the mirror and realized I am one of those little old duffers!!!!
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