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CLIMATE INFORMATION

The climate at D:FR is roughly classified as mid-elevation desert. It is neither as hot as nearby locales to the south and west, nor as cold as the higher elevation mountain and plateau country to the east. The Sunset Western Garden Book Climate Zones Map shows this to be a borderline transition zone between zones 11 and 12, as defined in the text of that publication. Zone 11 is mostly high-elevation Mojave Desert of southeastern California and southern Nevada, and Zone 12 is mid-elevation Sonoran Desert found in southern and western Arizona. Most Americans will be more familiar with the United States Department of Agriculture winter hardiness zone map. In placing D:FR on the USDA map, the location is defined as zone 9B, or the colder half of zone 9. The USDA uses average minimum winter temperatures as the baseline for this classification system. Zone 9 has lows most winters in the 20 to 30 degree range.

Specific climate information is not available at D:FR for the long term, because of its remote location and lack of nearby weather stations. The following information is based on observations over the past three years, climate data extended to the site from nearby locales with a weather station, and inference from ecological patterns and plant distribution.

High Temperatures Low Temperatures
Average high in July: 102 F (38 C) Average low in July: 75 F ( 24 C)
Average high in January: 62 F (17 C) Average low in January: 34 F (1 C)
Possible summer highs: up to 110 F (43 C) Possible winter lows: down to 22 F (-6 C)
Extreme summer highs: up to 117 F (47 C)* Extreme winter lows: down to 15 F (-10 C)*

*Note: these are extremes, unlikely to occur more than once a decade or so, if even that often

RAINFALL

The rainfall at D:FR averages about 8 to 10 inches (20 to 25 cm) per annum. The exact amount is unclear since no long-term weather records exist. This extrapolation is based upon existing weather records for the surrounding towns of Kingman, Yucca, and Wikieup, Arizona, as well as an interpretation of the rainfall required to support the native vegetation on and around D:FR. Rainfall is bimodal, meaning it tends to occur in two distinct seasons every year. There is a winter rainy season, usually in the months of January, February, and March, and a summer monsoon season in July, August, and September. Rainfall tends to be approximately evenly distributed between the two seasons. Rain is possible any month of the year, but is very unlikely to occur in May or June, and not very likely in October and November.

The sun illuminates the hills just east of D:FR minutes before sunset as a storm breaks up over the Hualapai Mountains. January 2001

Winter rains tend to be frontal in nature, with wet storm systems moving in from the Pacific Ocean over California and into the interior deserts of the Southwest. The nature of these storms is that they are generally cool and gentle, producing slow rains that last for hours or days, thereby giving the soil moisture levels a chance to recharge. Plant growth is sometimes inhibited by the cool temperatures, but the low evaporative rates preserve the soil moisture levels until springtime warmth arrives so that the plants may better utilize the available water. There are, however, many plants that grow only during the cooler months, and go dormant during the summer heat and drought. Rainfall in the late fall and early winter is responsible for the spectacular spring wildflower displays often featured in the travel magazines and tourist literature of the Southwest.

 

A 5-minute time exposure of a September 1999 monsoon storm shows a grove of Joshuas flanked by ocotillos and backlit by lightning in the distant mountains

 

Summer monsoons are the local word for powerful convective thunderstorms that pop up in the deserts at the times when there is adequate atmospheric moisture to generate them. The word "monsoon" is derived from the Arabic word "mausim", which means "season". The term is generally applied to areas with a distinct wet/dry cycle to the annual climate patterns. Climate aficionados will know that the monsoonal pattern reaches its peak development in India and Southern Asia, where well over one billion people depend on its annual arrival so that their food crops can be grown. The monsoon season of Arizona and the whole southwestern United States is not quite so pronounced climatically or as critical to the survival of humans living in the region, but it is critical indeed to the plants and animals of the deserts. If winter rainfall were the only rain that the region received, the biological diversity would be severely limited by the ability of creatures to survive 8 or 9 months of drought combined with high temperatures. As it stands, the summer monsoon breaks up the year into two wet and two dry seasons. This sort of a cycle tends to promote increased diversity in a desert ecosystem, since water, albeit still a limiting factor, is not nearly as severe a problem as it could otherwise be. In contrast to plants that grow during the cooler months, there are others that respond to summer moisture, remaining dormant during the cool season rains and growing and flowering only with summer and fall rains.

Moisture that generates these explosive thunderstorms arrives from one of two sources. The first source is, as expected, the Pacific Ocean. Somewhat surprisingly, however, the Gulf of Mexico contributes at least half of the annual summer moisture to the region, despite being much farther away and well to the southeast of the Sonoran Desert. Many times a strong clockwise flow of moist air sets up over the interior highlands of Northern Mexico and the Chihuahuan Desert of Texas and New Mexico, bringing huge volumes of warm, wet Gulf of Mexico air over Arizona. Combined with the desert heat, this air sets off atomic-bomb-like storms, mainly over eastern Arizona. D:FR is located a bit too far to the west and north to receive the full effect of summer monsoonal moisture, but there are days when the clouds from the southeast penetrate far inland and we get a large volume of rain in a short time. Yucca, Arizona, for example received 1.7" (4 cm) of rain in one afternoon in early July 2001, most of it in two storms lasting under 20 minutes each. These storms are dramatic and unpredictable, and tend to cover limited geographical areas. The storms that pounded Yucca, only about 15 miles from D:FR, left us high and dry with no rain to speak of. The reverse is likely to be true at other times, however.

A brief but heavy hailstorm whitens the ground after passing in January 2001

Snowfall is possible but rare at D:FR. On average, it tends to occur only once every two to three years. Then it is likely to be only 2 to 4 inches (5 to 10 cm) and to melt off within a few hours of sunrise. The 3000-foot (900-meter) elevation at D:FR means that snow is ephemeral and rarely heavy. Nearby locations in the Hualapai Mountains may receive snowfall from November through April, and may be snow-covered for weeks or months on end in mid-winter, especially on the north-facing slopes. Hail is associated  with both winter and summer storms on occasion, and may carpet the ground in white after the passage of a particularly strong cell.

WIND

Winds are moderate to light most of the year at D:FR. The windiest season tends to be winter, when chilly winds may set up out of the north for days on end. The strongest winds are usually associated with downbursts of cold air from a thunderstorm. Brief gusts of up to 50 or 60 miles per hour (80 to 100 kph) may damage trees, roofs, airplanes, and wind-generation equipment, but rarely last for more than a few minutes as the storm passes overhead. Local whirlwinds known as "dust devils" may occasionally pass by on a hot summer afternoon. Caused by unstable hot surface air spinning as it rapidly rises, they are rarely large or damaging, and a pleasant quirk of the desert, providing momentary relief from the blistering heat.