Cold weather also puts immense strain on the heart. Low temperatures cause your blood vessels and arteries to narrow, restricting blood flow and reducing oxygen to the heart. Your heart must pump harder to circulate blood through the constricted blood vessels. As a result, your blood pressure and your heart rate increase.Your blood flow slows when the weather is cold, which can make your heart muscle to try harder to get the oxygen-rich blood it needs. Avoiding situations that might makes things worse can limit your chances of having a heart attack.