Quote Originally Posted by Doc Alan View Post
Blood pressure does vary naturally from day to day and in different situations – hence the need for accurate measurement, certainly before treatment is contemplated.
Generally it tends to rise when it’s cold and fall when it’s hot. Arteries constrict ( get narrower ) in cold and dilate ( get wider ) in heat, to maintain body temperature. These effects are temporary, just like other influences on blood pressure, like drinking coffee, physical activity, and stress – as long as they are not extreme or prolonged.
Extreme hot and cold temperatures affect the cardiovascular system, especially in the elderly and those already with risk factors such as hypertension, at least short term. Heatwaves increase cardiac deaths, once the body’s attempts to dissipate heat are overwhelmed. Sweating and dehydration can raise blood pressure, or ultimately decrease blood volume and increase heart rate, causing heart failure and fall in blood pressure. In the UK there are more heart attacks in winter. Exposure to cold without protection progressively increases the chances of a heart attack – due in part to constriction of blood vessels and increased tendency of the blood to clot.


Okay. My wife's veins on the back of her hand dilate on warm / hot days though she doesn't have a lot of fat on her so I think it is more obvious.