Climate: HOT summers! Overwhelmingly people recommend Serve shirts with the ventilated sides and light-weight golf pants.
ECCO shoes don't do well in the extreme heat of the desert. The soles melt on pavement. Dr. Martens or Clarks or shoes with thick soles do better.
This mission has biking and cars. But with biking in the heat, a camelback is SOOOOO nice to have.
It does get down to the low 40s in the winter, so gloves for the chillier time might be nice, but maybe wait until the missionary is there and knows what circumstances he/she will be in.
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People serving in hot missions highly recommend a hydration backpack. CamelBak is the brand mentioned most, but there are plenty of lower-cost options as well.
Serve shirts have a ventilation panel in the side of the shirt making them noticeably more breathable. Missionaries serving in hot or humid places absolutely RAVE about this feature. The most popular shirt for hot-climate missions, for sure.