According to some studies menstrual cycles are affected by sunshine and there is a link between vitamin D exposure and increased production of a follicular stimulating hormone (FSH), which leads to higher ovarian activity which can cause frequent and longer periods. The heat in summer causes fatigue, exhaustion and dehydration and these along with the hormonal changes that can cause bloating, water retention and mood disturbances before and during periods can make the periods tiresome and difficult to cope with.