Subtle changes in running - weather related?

I'm curious and haven't seen much posted on this topic.

One day my XJ will be running just absolutely perfect. Another day, it is running well, but just seems a "bit off." Nothing serious, just not perfection - a minor stumble here or there, etc. Could it be related to humidity, temperature (65f as opposed to 90f, etc)?

Is this possible, or am I imagining this?

 

I would think humidity and dew point impacts the combustion... cooler drier air goes boom better than warm moist air.

 

Also gas. Fuel quality can vary, after all. And different station's fuel isn't always the same to start with anyways.

 

Temperature definitely affects the performance. Some bikes are cold blooded. The bike I used in the MSF course was a Honda imported from Brazil, and it must have been set up for more tropical climate, because it needed choke for like 5 minutes first thing in the morning. It simply didn't like the cold.

 

I get that, however, sometimes I notice minor differences one day to another within the same tankful. I'm guessing temperature, humidity, and perhaps even my mood, are all factors.