The Autumnal Equinox is here. Monday, September 22 is the first day of Fall. Imperial Valley weather may not feel fall-like yet. The National Weather Service says there is a 20 per cent chance of rain on Monday and there may even be some thunderstorms. Near to slightly below normal temperatures are expected Monday before heating up midweek. A low pressure system will move through the region by the end of the week and that willed to cooler temperatures and possibly renewed rain chances. Expect highs near 100 before the cooldown by next weekend.