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Date: 6/20/2016

Title: Hot Start to Summer

Hot temperatures in the Desert Southwest made headlines this past weekend as temperatures soared deep into the lower 100s in many areas of California, Nevada, Utah and Arizona. The right combination of the longest days of the year, low pressure in the Pacific Northwest and building high pressure over the central U.S., led to the extreme heat in the Desert Southwest. 
While there will be some very modest relief from the heat in the Desert Southwest in the coming days, the heat will persist while expanding to the east and north.
Beef producers in the south and central areas of the nation should be prepared for some of the Desert Southwest heat to expand into the central and eastern areas of the U.S. over the next week to ten days.  While the heat will not be as extreme as experienced in the Desert Southwest, stock growers should be prepared for some summer time heat as we go through the last days of June.
For folks in the Northern Plains, Great Lakes and northern areas of the Corn Belt, the heat will not be as severe as the northern branch of the stream will send some weak cool fronts south across the region keeping temperatures from being too hot over the few days.

One result of the June heat in the Desert states will be the initiation of the “Summer Monsoon” season in the Southwest and Rockies in the coming weeks.

The summer monsoon season in the desert states and Rockies is driven by the sun heating up the deserts and the Pacific Ocean at different rates, with desert surfaces warming more quickly than the ocean. The warm land creates low-pressure zones as hot air rises as the hot air is less dense. Once this pattern establishes across the region, the winds shift as air pressures begin to change over the land and oceans.

With this shift in the winds, the monsoon begins in northern Mexico in May. The moisture-laden air travels north to Arizona and New Mexico, encouraged by the pressure difference between the hot, parched southwestern air and the cooler Mexican air.

The monsoon moisture flow then continues to spread north bringing needed and cooling rains to the Desert Southwest in late June and early July and then expanding as far north as the central Rockies and High Plains by the middle of July.

The graphic below shows the average time of year when the summer monsoon season begins.


While it may seem counter intuitive, the extreme heat and dryness actually initiates the wet and cooler monsoon season. This is also experienced in other parts of the globe. The extreme heat in May and early June in India will be followed by their own monsoon season.