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Species Spotlight


“Monsoon”

by Doug Moore

A growing pile of cotton balls floats just off the summit of Mt. Wrightson. I watch the china-white clouds as I drive I-19 toward Green Valley, wondering if they will build and darken into an afternoon thunderstorm. The prospect for rain in Madera Canyon looks good today; our summer rainy season is in full swing.

In southeast Arizona we have an extra season that follows the bone-dry summer heat of May and June. A shift in the prevailing northwesterly winds to the south in July announces Wet Summer, locally called the “Monsoon.” Tropical moisture is drawn into the region and the humidity rises sharply. The moisture combines with intense day-time heating over our Sky Island Mountain ranges to produce spectacular thunderstorms. Rainfall resulting from these storms is usually local, but can be remarkably heavy. Higher, cooler elevations generally receive more rain. Monsoon rainfall totals for the Santa Ritas and Madera Canyon are often two to three times the totals for the Santa Cruz Valley below.
Inducing clammy, clinging clothes and rendering evaporative coolers impotent, monsoon humidity is viewed by some as a curse. But it is a tremendous blessing to plants and animals! Summer rains stimulate productivity that rivals that of the winter rains. And, I don’t know anyone who doesn’t revel in the earthy smells and coolness of a post-thunderstorm evening as a brilliant Arizona sunset blazes through remnant clouds!

With the rains of Wet Summer, Madera Canyon transforms into a sub-tropical wonderland. Trees, shrubs and grasses green up and sprout new growth, while a host of summer plants add to the verdant mix. Dormant underground tubers and bulbs, like Flame Flower, Melon Loco and Nodding Onion, awaken and stretch for sunlight. Seeds of summer annuals, like Morning Glory and Arizona Sunflowerweed, germinate with the warm rains. A dozen varieties of annual and perennial vines festoon shrubs and trees. Shades of green are the canyon colors of the season, punctuated with the bright colors of summer flowers.

Summer rains also stimulate animal activity in the canyon. Insects emerge from eggs and pupae to take advantage of the summer bounty. Grasshoppers and butterflies suddenly seem to be everywhere. Close inspection of plants and flowers reveals all sorts of beetles, ants, bees, flies, spiders and other “bugs”. Fantastic caterpillars munch on leaves; stealthy praying mantises stalk their meals. Water beetles, back swimmers, dragonfly and damsel fly larvae, and a host of other invertebrates inhabit creek pools. At night the air is filled with moths and beetles searching for food or each other. Scorpions, centipedes, wind scorpions, and hunting spiders come out to hunt after dark. Many mammals, birds, reptiles, and amphibians also become more active to take advantage of the seasonal bounty, completing the complex canyon web of life.

“Monsoon” is arguably the most interesting time of the year for nature watching in Madera Canyon and should definitely be experienced! But there are things to watch out for! Danger from lightning and flash flooding is very real; morning activities before thunderstorms build are often the safest bet. Be aware that storms often form on the Santa Ritas out of sight from Madera Canyon, and later drift full-force over the rim to catch hikers unaware. Cooler, moist temperatures can make animals more active. Bears and rattlesnakes live in the canyon; pay attention to where you step and to your surroundings at all times. Poison Ivy grows in many places along Madera Creek. Biting chiggers are present, particularly in the grassy meadows around Proctor and White House. Mosquitoes are often numerous at dawn and dusk anywhere in the canyon. A good insect repellant is recommended! Cooler temperatures and humidity can also fool you; take plenty of water and stay hydrated! Enjoy the monsoon’s bounty, but stay safe!


Monsoon "golden rain" in the Santa Cruz valley - Frank Walsh


Madera Creek running full after a monsoon rain - Maggie Ramlow