How might higher levels of development of a country be related to temperate locations??
Have you ever spent any time in a climate in which the temperature always ranges from 90 to over 100 and the humidity is about the same? It's very difficult to do much work in this kind of climate. Mosquitoes thrive in these locations and spread diseases too. Hot desert climates also don't yield crops and are nearly impossible to live in. What energy people have is spent just getting food.
Very cold climates, where the temperature rarely goes above freezing and often is below 0 degrees also are difficult for people. No crops grow and the inhabitants depend on very limited food supplies.