The natural environment

The Treasure Valley itself and most of the area’s population lies in the Snake River Plain, a wide flat area along the Snake River that stretches across southern Idaho from Wyoming to Oregon.

Most of the plain is classified as dry, mid-latitude desert which, according to Bureau of Land Management educator Barbara Forderhase, is high desert on the northern edge of the Great Basin Desert. The areas to the northeast and southwest of the valley are identified as warm summer continental climates. In plain English, this means residents in the Treasure Valley can expect cold (often freezing) winters, hot summers and low levels of precipitation.

As far as vegetation goes, the area is classified as “shrubland” and the most common shrub of the land is sagebrush, a plant that thrives in the temperate desert of the Western United States. The land between the sage and other shrubs, including winterfat, is filled with native bunchgrasses and exposed soil. In many areas, the desert has also been colonized by invasive cheatgrass, a non-native species which increases fire danger.

According to Forderhase, almost 260 species of animals call the area around the Snake River in Southwest Idaho home. This total includes 45 different mammals, 165 species of birds, 25 kinds of fish, 16 reptile species and 8 species of amphibians. The largest and most visible of these include mule deer, pronghorn antelope, coyotes, badgers, foxes, bobcats and mountain lions.

Bringing water to the desert

Those who move into the Treasure Valley may not immediately notice that they are moving into a desert, because they’re among the lush green lawns and farmlands that surround most Treasure Valley communities. This greenery comes from Federal Bureau of Reclamation efforts to manage the irrigation needs of the area, said John Redding, a public affairs specialist for the bureau.

For more than 80 years, the bureau has worked with local organizations to operate a complex network of dams and canals to manage floods and provide water for agriculture, area residents and businesses, Redding said.

According to Redding, without the efforts of the Bureau of Reclamation the valley would be dry and agriculture would be minimal.

“You would not have the growth, the business, the industry, the people that you see today,” Redding said. “It would be a high desert. (A) wild sort of country without a population base.”

Many Treasure Valley cities are located near rivers which, when combined with irrigation efforts, increase the availability of water and the level of greenery in the surrounding area. In fact, Boise is known as the “City of Trees” and is the oldest of 11 Treasure Valley cities that have earned the National Arbor Day Foundation’s Tree City USA designation, a label given to cities that have shown a concrete commitment all things arboreal.

Temperature and precipitation

All temperatures are given in degrees Fahrenheit and are monthly averages. The hottest month is taken from the average high temperature, while the coldest month is taken from the average low temperature. Seasonal averages are taken from the average high only. All precipitation is given in inches. The location of the monitoring station is given in parentheses after the county name.