North American Monsoon: June 15 – September 30
June 30th, 2018Monsoon Season or “The Monsoon”
Definition: Large scale weather pattern that causes summer thunderstorms to develop. Moisture transported northward from Gulf of Mexico and eastern Pacific due to a reversal in wind patterns, resulting in a distinct “rainy season” over western North America. Thunderstorms with heavy rain can cause severe flooding. These storms can be powerful and sudden.
Typical Monsoon Season:
• Rainfall is not continuous over space or time
• Varies considerably and usually comes in distinct “burst” periods of heavy rain
• Accounts for over 50% of annual precipitation in northwest Mexico and Southwest U.S.
Associated Hazards
• Deadly, unexpected lightning
o A clap of thunder indicates a thunderstorm is within 10 miles
o Lightning can strike up to 60 miles away from the nearest rainfall • Local damaging straight-line winds (100+ mph)
• Flash floods, especially at low water crossings
o Water can rise quickly downstream from heavy rain, even when the thunderstorm is miles away
o Six inches of fast-moving flood waters can knock you off your feet
• Excessive heat (higher humidity and hot temps)