Annual Weather

At 2,400' the Arboretum offers a cool, shady oasis during Arizona's famously hot summer months. Want to know another reason it's cooler at the Arboretum? Towering 150-foot tall eucalyptus trees (also pistachio, cottonwood, sycamore and pine) line the Main Trail and provide shade, too! You’ll be comfortable wearing shorts and lighter clothes during much of the year, but plan to dress for the summer heat from May-through-August, and bring along a jacket (gloves and hat are a good plan, too) for an early morning walk during January and February.

Nighttime temperatures drop into the 30s during winter months, and the coldest mornings can be surprisingly raw until the sun climbs high enough to warm the gardens and trails. If you live in the Phoenix area and want to see snow, watch the forecasts during December, January and February. If snow is predicted below 4,000 feet, you might just see a mantle of white crowning Picketpost Mountain, the former volcano which looms above the Arboretum.

And if you love that distinctive smell the Sonoran Desert has following a good rain, plan an afternoon visit in July or August during the summer rainy season. Afternoon “monsoon” rains release the fragrance of essential oils in the leaves of creosote bush and eucalyptus trees — a seasonal smell you’ll want to experience for yourself. Significant rainfall to the east in our neighboring town of Superior (like an inch or more from one quick thunderstorm) brings a rare sight when ephemeral streams such as Silver King Wash run bank-to-bank with a roiling torrent of stormwater.

Below is a listing of average daily temperatures and monthly precipitation:

Boyce Thompson Arboretum State Park Average Daily Temperature (Degrees Fahrenheit) & Monthly Precipitation (Inches)
Month Temperature Precipitation
High Low
January 61° F 43° F 2.25"
February 64° 45° 2.33"
March 69° 48° 2.45"
April 77° 54° 0.74"
May 85° 62° 0.48"
June 96° 72° 0.30"
July 98° 75° 1.90"
August 96° 74° 2.82"
September 72° 71° 1.79"
October 82° 61° 1.48"
November 70° 50° 1.73"
December 62° 44° 1.97"

Note: Weather data is provided as a general guide only. Arizona State Parks assumes no responsibility for any loss resulting from use of this information.