According to the MayoClinic.com, blood pressure increases in the winter and decreases in the summer in most people. The diameter of blood vessels constricts in cold temperatures, causing the heart to work harder to push blood through the veins and arteries. Both systolic (blood pressure when the heart contracts) and diastolic (blood pressure reading while the heart is at rest) readings increase during colder weather.
Cold weather impacts the elderly more than other age groups. Physicians recommend older persons and those with chronically high blood pressure closely monitor their blood pressure during the winter.