Most women will experience hot flushes ('flashes' US) when going through the menopause. They're often described as a sudden feeling of heat that seems to come from nowhere and spreads throughout the body.
It's assumed that they are in some way linked to changing levels of estrogen, but how this mechanism operates is unclear.
“Hot flashes and other vasomotor symptoms accompany the menopausal transition. While many sources continue to claim that hot flashes during the menopausal transition are caused by low estrogen levels, this assertion was shown incorrect in 1935 and, in most cases, hot flashes are observed despite elevated estrogen levels. The exact cause of these symptoms is not yet understood, possible factors considered are higher and erratic variation of estradiol level during the cycle, elevated FSH levels which may indicate hypothalamic dysregulation perhaps caused by missing feedback by inhibin.”