However, each woman may experience symptoms differently with some having few and less severe symptoms, while others have more frequent and stressful ones. Usually hot flashes start before a woman's last period. For 80 percent of women, hot flashes occur for two years or less. A small percentage of women experience hot flashes for more than two years. These flashes seem to be directly related to decreasing levels of estrogen.
Hot flashes vary in frequency and intensity for each woman.
In addition to the increase in the temperature of the skin, a hot flash may cause an increase in a woman's heart rate. This causes sudden perspiration as the body tries to reduce its temperature. This symptom may also be accompanied by heart palpitations and dizziness. Hot flashes that occur at night are called night sweats. A woman may wake up drenched in sweat and have to change her night clothes and sheets.