However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing, kidney problems (such as change in the amount of urine). This is not a complete list of possible side effects.
They are more active when it is cooler, but they can and do come out of hiding at any time of the day. Here in the desert, Arizona Rattlesnakes can easily overheat and die if they cannot find a cool place to keep themselves cool.
As mentioned earlier, most parts of Arizona do not observe daylight saving time, so these parts remain on MST. The Navajo Nation lands, which extend to the states of Arizona, New Mexico and Utah, observe daylight saving time from April to October.