Service Tire System Soon--Followup

Thanks for all the replies to yesterday’s posting. We are in Mesa, AZ where temps currently are 40 F nights and 60+F days. Tires were warm from freeway trip back from tennis match with 6 aging men and read 39 PSI, which is about right for my previous cold tire setting of 36 PSI. Last checked the spare in October and brought it back up to 60PSI. We have the cheapie sensor system, it only tells us one of the tires has low/high pressure, not which tire. Will again check the tires cold as you recommend and drop the spare–a real pain–and check it. Will take it to our wonderful personal mechanic, and former neighbor, upon our return to Nebraska. You guys are great!
Dan