[wsc981]

> There does seem to be a mild correlation with outside temperature. Could some places just be "too hot to think"?

Well ... perhaps in some way:

    Since 1991 there has been the presumption that persistent heat affects the IQ over 
    generations. It was initially assumed that living in lower temperatures requires a higher
    physical fitness and causes higher social demands. Richard Lynn, a professor at the 
    University of Ulster in Northern Ireland, also assumes that the colder temperatures 
    increase the brain volume. Whether brain size is at all related to intelligence, is 
    controversial.

    In general, a hot climate is considered a disadvantage for the development of 
    intelligence. The reason is nowadays primarily seen in the high physical energy demand 
    and the resulting stress.

Source: https://www.worlddata.info/iq-by-country.php

Another study suggests infectious diseases might be a cause for lower IQ scores. In that case, perhaps infectious diseases spread more easily in hot climates?

See: https://www.scientificamerican.com/article/why-is-average-iq...