Visible passes need the station in sunlight while you are in darkness — tonight that window opens around 8:22 PM.
The International Space Station orbits about 400 km up and completes a lap roughly every 90 minutes, so it passes over Phoenix, AZ several times a day. Most of those passes are invisible.
You can only see the station when two things are true at once: the ISS is in sunlight, and you are in darkness. That confines visible passes to roughly the two hours after sunset and the two hours before sunrise. In the middle of the night the station is usually in the Earth's shadow — still overhead, still invisible.
Best evening viewing runs from about 8:22 PM to 9:54 PM, and again before dawn from 5:13 AM.
The ISS appears as a steady, fairly bright point moving from west to east. It does not blink — anything flashing is an aircraft. A good pass lasts four to six minutes and can outshine every star in the sky. It often fades out mid-sky rather than setting, which is the moment it crosses into the Earth's shadow.
The live map tracks the station and 156 other visible satellites in real time from your location, and will scan the next 24 hours for passes with rise time, direction, maximum altitude and duration.
Also for Phoenix, AZ: what's in the sky tonight →