"But it's a dry heat."
"Yeah, and so is my oven."
That's an old Arizona joke, but like many yarns, its roots are based on the truth. Come to Phoenix in June and you'll swear you're in an oven set to broil. But, it is a dry heat. I'll take 110 degrees and 7% humidity in Phoenix to 85 degrees and 95% humidity in Washington DC any day. Other people like damp, jungle heat and days of below freezing temperatures and overcast skies.
In Arizona, you can usually bet on a sunny day. Arizonians see the sun something like 360 days a year. Not too bad. But that doesn't mean we don't get rain. We do. Sometimes. And sometimes, it can be substantial. Visit Tucson in late July for the monsoon season and you'll see some nice thunderstorms.
And there are places in Arizona that get cold. The White Mountains and Flagstaff get snow every year (yes, we do have skiing in Arizona). There are places in Arizona that within a two hour drive the temperatures can range from 80 degrees down to below freezing.
The bottom line about weather in Arizona: it's usually nice and sunny, but you need to know what to expect. Going for a thirty mile mountain bike ride in Phoenix in August might not be the best plan.
Wherever your next adventure may be, you can view up-to-date weather forecasts and view local radar to make sure you're prepared.
Want to see how much rain your favorite trail received during the latest storm? It's easy to do (as long as your favorite trail resides in Pima or Maricopa counties). Here are links to maps containing rain gauges that show data real-time (or at least close to it). I've used the Pima County site with great results. One of the best times to go to Chiva Falls is after a summer monsoon. Previously, it was difficult to know if the area around Chiva actually received any significant amount of rain. Now, I just go to the website, click on the gauge near Chiva Tank and know for sure. It's awesome. No more guess work. I have only found this data available for Pima and Maricopa Counties. If anyone knows were I can find this for Arizona's other counties, please send me the links.
July 21 update: I found this great website from a KOLD news report. Another website you can visit to track rain amounts is rainlog.org. This website surveys people around Arizona who have set up their own rain gauges to calculate rainfall amounts. It's another great resource!
The best local radar links for southern Arizona are KOLD Channel 13 and KVOA Channel 4 Interactive Radar where you can plot the address you want to check the weather for, zoom, pan, show terrain, maps or anything else you usually do on Google Maps. It's great.