While hot flashes (or flushes) are very common in perimenopause, not all women experience them, and not all flashes are of the same intensity. Hot flashes can be as mild as a light blush or severe enough to wake you from a sound sleep (called night sweats). Most hot flashes last 30 seconds to 5 minutes. They usually disappear within a few years after menopause. However, up to 10-15% of women experience hot flashes for years.