This year, New Mexican officials have a message for farmers who depend on irrigation water from the Rio Grande and other rivers: Unless you absolutely have to plant this year, don’t.

Years of warming temperatures, a failed rainy season last summer and low snowpack this winter have combined to reduce the state’s rivers to a relative trickle. The agency that controls irrigation flows on the Rio Grande forced the issue. To conserve water, it opened its gates a month later than usual.

Severe drought — largely connected to climate change — is ravaging not only New Mexico but the entire Western half of the United States, from the Pacific Coast, across the Great Basin and desert Southwest, and up through the Rockies to the Northern Plains.

In California, wells are drying up, forcing some homeowners to drill new ones that are deeper and costlier. Lake Mead, on the border of Arizona and Nevada, is so drained of Colorado River water that the two states are facing the eventual possibility of cuts in their supply.