Southwest Monsoon 2025 Set To Kickoff With A Tropical Boost Next Week

Yahoo

19 hours ago

The annual Southwest monsoon season is getting ready to kick into high gear as July begins.
We've already had spurts of heavy rain across parts of the region, including in New Mexico over the last week.
Wetter Pattern Ahead: A pattern change will be underway across the western U.S. through the weekend and into next week. The result is that the Northwest will see a modest heat wave that will slowly fade through the week ahead. Underneath that heat dome, a weak low pressure system will approach the Pacific Southwest. This will increase the flow of moisture across the region next week.
An extra kick: Extra moisture is likely coming from the tropics. A tropical system is likely to develop south of Mexico through the weekend and into next week. While some details are still uncertain, most computer guidance brings whatever this system becomes closer to Baja California next week with a large cocoon of moisture.
(MORE: Further beef up your forecast with our detailed, hour-by-hour breakdown for the next 8 days – only available on our Premium Pro experience.)
The monsoon is a seasonal wind direction change, not an individual thunderstorm. Monsoon is a term used in multiple parts of the world that refers to a seasonal wind shift that has wet and dry phases. In the Southwest U.S., winds change from a more westerly direction during the dry phase to a southerly direction during the summertime wet phase, which pumps moisture from the Eastern Pacific and Gulf into the region.
The start of the monsoon varies from year to year. June 15 is when the monsoon officially begins, but in many areas, it takes until late June or even July for the coverage of storms to grow. The thunderstorm activity then varies in intensity from day to day or week to week through August and September.
The monsoon is the main driver of rain for the Southwest. Most of northwestern Mexico and the southwestern U.S. receive over half of their annual precipitation from the monsoon.
The monsoon also brings dust storms, flooding and lightning. Thunderstorms can generate huge dust storms known as haboobs that can lower visibility and cause air quality concerns. Canyons and arroyos can become victim to flash flooding even if it isn't raining. Floodwaters can travel many miles downstream through canyons. Early in the season, prolific lightning can create fires until the ground is moistened.
Hurricanes can cause rapid upticks in monsoonal moisture. Occasionally, remnant spin and moisture from former Eastern Pacific tropical storms or hurricanes can be pulled into the Desert Southwest, enhancing heavy rainfall. Two tropical systems – Hurricanes Kay in 2022 and Hilary in 2023 – have caused flooding in California.
Jonathan Belles has been a digital meteorologist for weather.com for 9 years and also assists in the production of videos for The Weather Channel en español. His favorite weather is tropical weather, but also enjoys covering high-impact weather and news stories and winter storms. He's a two-time graduate of Florida State University and a proud graduate of St. Petersburg College.