90 cherokee cold and damp running problem

My daughter's 1990 cherokee six cyl. 4 liter has a problem running at anything above idle when it has rained or is quite damp outside. Until the coolant temperature reaches about 110 deg it stumbles badly when given throttle. could it be the O2 sensor? Don't really know where to start looking.

How many miles on it? If the O2 sensor is original more than likely it hasn't been working for years...along with some other so called anti-pollution items.

How old are the spark plug wires, distributor and rotor? It's common for these items when extremely worn/old to cause problems when under conditions of high humidity or rain.

I agree check wires plugs Dist cap also check your coil they act bad to moisture when they start to go bad. As for oxygen sensor does it show a code?