It's also one of the reasons more heart attacks occur in cold weather - cold increases blood viscosity. An increase in viscosity means more pressure required to pump blood.rich01 -- I've heard something about blood viscosity. It has something to do with the outside temperatures - or something. It's the reason that someone who visits Los Angeles, coming from Massachusetts, sees 40 degree (F) days as t-shirt days, while Los Angeles natives bundle up. It's why this Angeleno (slang for someone from Los Angeles) can go to New Jersey in August, handling the 100 degree (again F) weather much less uncomfortably than the New Jersey natives.
If it's blood viscosity that makes the difference (is it?), then let me apologize when I responded to your comments about viscosity with my rant about 'blood thinners.' (Part of my reason for my lecture was an ad that I saw on eBay a few years ago. It was an ad for a meter that was used to test 'blood viscosity' - with the seller assuming that this had something to do with viscosity because it tests for blood thinning).