Weather
Fair weather
patterns predominate in the arid Southwest. In early spring, the
storm track tends to shift north of the region, and high pressure
typically brings consecutive days of dry, mild, sunny weather.
This pattern becomes even better established by mid April, and
persists throughout May - the region's driest month on average,
with little measurable precipitation likely. By July the monsoon
arrives, bringing higher humidities and a cycle of afternoon thunderstorm
activity that usually lingers into early September. Toward the
end of this month the atmosphere typically becomes more stable
and dry again, and barring any influences from the jet stream,
fair weather rules into October and November.
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Spring
flurries & old snowpack, Mogollon Mtns at 9500'
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Storms that
do affect spring and fall thru-hikers tend to be short-lived and
any precipation tends to come in the form of rain. Temperatures
at the highest elevations can occasionally support snowfall during
these storms, but significantly accumulating snow is unlikely
except perhaps in late fall. Wind storms can occur at any time,
especially during spring in New Mexico, where gusty afternoon
winds are often accompanied by clear skies and very low humidity.
Dry air allows
for a wide range between daytime high and nighttime low temperatures.
For thru-hiking east in spring or west in fall, expect desert
high temperatures in the 70's and 80's F, with occasional 90+
degree readings (less likely in fall), and overnight lows mainly
in the 40's and 50's. Mountain high temperatures tend to run 10
to 15 degrees cooler than the desert. Regardless of altitude,
subtract ten degrees all around in mid to late autumn (although
the lowermost Sonoran desert can remain quite warm throughout
fall).
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| Fair
weather cirrus & Weaver's Needle, Superstition Wilderness |
Dry air also
amplifies the sun's heat and UV, making exposed surfaces (including
skin and clothing) feel much warmer than the air temperature.
To an extent, though, this heating effect is negated by the body's
ability to quickly evaporate sweat in low humidity, and exertion
is often well tolerated in desert temperatures in the 80's and
even 90's. The most important consideration in such conditions
is adequate fluid and electrolyte replacement to insure that beneficial
sweating continues to occur. In addition, find shade from time
to time, wherever possible, and wear a wide-brimmed hat and long
sleeves to minimize exposure when the sun is highest. See the
Precautions section for
a few additional clothing tips.
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| Hail
in camp; freak spring thunderstorm on the AZ-NM border |
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