My best climate would be a climate where there is at least some variation in temperature, but maybe not any frost or snow, and average high temperatures in warmest month would be around 30 C and average low temperatures in coolest month would be around 8 C. The west season (summer) and dry season (winter) would also be good, rather than uniform rainfall all year long. Or a semi-arid or desert climate.
Waco, Texas?
Something like that. A climate where there is at least 25-45 nights below freezing annually, and at least 3-15 days above 40 C annually.
I'm not sure your ideal climate necessarily exists. Most places that drop below freezing that often are going to have some amount of snow at some point over the course of the winter. Also, very few places that have that many days over 40C (104F) have an *average* high in the warmest month of only 30C (86F). Some parts of Europe might have a summer temperature climatology like that but for the most part you don't really get that kind of extreme variation in the US. Yes, heatwaves are a thing, but there are very few places that have that many 40C days annually and most of them are either in the Plains or the desert southwest, where July highs are typically in the 90s F (33-38C roughly) at least.
I will second Scott though and point you towards the southern Plains or Texas for a place in the US that comes closest to every category you described.
