Mower won't start with a lot of moisture in the air. humid damp outside. Will crank but won't fire. Put in sun with hood up for twenty minutes,fire right up no problem

Hi,
You have a Kohler Command single cylinder engine in you machine. The carb is sensitive to varnish buildup which leans the mixture. A damp day exacerbates the situation. Cleaning the carb should help. The choke is separate so make sure it fully engages. The engine is also sensitive to being shut off with the engine revved up. You shoule throttle down for a few seconds before turning it off. It will slowly shear the flywheel key if you do not. A partially sheared key can affect the cranking as well.
Peace,
Clarke

Thanks Clarke for the good advice. I will check into what you have suggested. Keith