Please excuse the brief intrusion of a Honda enthusiast in your forum!
I run the FAQ for rec.autos.makers.honda and over the past couple of months we have been getting the usual spate of questions about hot weather starting problems. This is a known Honda foible and we have the answer ready. Occasionally however we get the odd Mazda owner asking the same question, and I have no idea if other Japanese manufacturers use the same main relay system that has so long been the cause of such problems in Hondas.
Here is a FAQ on the subject:
formatting link
Does any of this apply to Miatas? Mazdas in general?