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TUCSON' FIVE SEASONS

I've heard many people say, "I'd never live in Tucson... You have no seasons." I've also heard people say, "Tucson has only one season -- Hot," usually followed by a chuckle. Next time you hear this, tell the misinformed person that Tucson actually relishes 5 seasons, one more than everyone else! Besides the images below, check out "Annual Change" to see how one spot changes in appearance through the year.

SPRING: Late February - April. Days are usually warm and sunny with cool nights (however, the occasional cold snap can still come through; it snowed in Tucson on Easter in 1999). This is peak wildflower season, with both "winter" wildflowers and shrubs splashing the desert with color. Toward the end of the season the leguminous trees and the cactuses (even the occasional Saguaro) are blooming. Migratory birds fly through Tucson, using the riparian (wetter) areas as corridors north. Many of the migrating birds stay (e.g., Black-chinned Hummingbirds and White-winged Doves) to breed. Many of our local animals are breeding. Reptiles come out to soak up the warmth and breed. Butterflies and other insects take advantage of the good weather and abundant food.

DRY SUMMER: May - June. Days are usually hot, and dry, but the nights are still cool. This is when the majority of the saguaro (and other columnar cactuses) bloom, and the bats that pollinate them (e.g., Lesser Long-nosed Bat) migrate into the area from Mexico. Later in the season, the cactus fruits Jojoba seeds, and legume tree pods ripen, providing food for people and animals at a critical time of year (hot and dry). This is when the buzz of cicadas fills our ears.

MONSOON SUMMER: July - Early September. We enter the monsoon period officially after 3 consecutive days with daily mean surface dew points of 55 degrees F or greater (representing an influx of moisture into our area). The increase in dew point occurs when the prevailing winds shift from westerly to southeasterly, bringing more moisture in from the Gulf of California (mostly) and Gulf of Mexico. Days often begin clear and very warm, but as the heat of the day builds, huge clouds build and tower above (see Why it Rains), cooling the temperatures somewhat (but increasing relative humidity) and often dumping huge quantities of rain in a very short time. This is the time of wind and dust, flashfloods and lightening. Summer rains trigger the appearance of many animals. For example, many of our amphibians emerge above ground and begin their hasty breeding cycle, taking advantage of the massive flights of new ant and termite queens and males, among other insects. Summer rains also trigger a second wildflower show, this time composed of "summer" wildflowers and shrubs. Wonderfully-sweet Prickly Pear fruit ripen (see in picture to right). Birds begin moving through and out during their fall migration.

FALL: Late September - November. Days are still hot at the beginning of the season, but nights become cool again as the humidity leaves the area (see the bottom of Meteorological Concepts). Things begin to quiet down. Reptiles begin seeking shelter. Wintering hawks and sparrows begin moving into the Tucson area. Desert Broom blooms, much to the agony of allergy sufferers but much to the pleasure of the many butterflies that visit Desert Broom. Freezing temperatures and even snow can occur late in the season. Octotillo leaves turn orange and drop off (see picture). Toward the end of the season, as temperatures cool off, animals that were more nocturnal during the summer now begin to become more diurnal and visible. This is when many of the wildflower seeds are waiting for cues to germinate. If the rains are right, we can expect a magnificent show; if the rains are not right, many of the seeds will wait for another year.

WINTER: December - Early February. Days are usually clear, except when fronts move through bringing clouds and rain (or rarely snow), but daytime temperatures plummet to the 60s and nighttime temperatures average in the upper 30 and lower 40s. This means we often have to scrape ice off our windshields. This is also the season that we listen to the Northern Mockingbirds sing all night long, as they establish their territories and show off their song repertoires. Gila Woodpeckers and Flickers, lacking the beautiful voice of the mockingbirds, tap loudly on anything that will resonate (such as trees, houses, light poles, and other metal objects) to establish territories. Phainopeplas adorn the treetops between feasting on Desert Mistletoe berries. Many plants drop their leaves (e.g., Velvet Mesquite and other leguminous trees), but the winter rains may trigger leafing in shrubs such as Brittlebush and Ocotillos. Early wildflowers begin to bloom as harbingers to the spring.

Also see Tucson Climate Statistics for precipitation and temperature data by month.