That’s not smoke; that’s steam. It is coming from Salt River Project’s Santan Generating Station.
Here’s how that works, according to SRP, the utility cooperative that powers most of Gilbert:
SRP uses natural gas to power a combustion turbine. The process produces exhaust heat. That is captured to create steam, like boiling water in a pressure cooker. The exhaust is then filtered through catalytic cleaning systems before being released through a stack.
The reason you see it so well on cold days is the same reason you see your breath on cold days or your hot shower produces so much steam on a cold morning. It has to do with the air temperature and the amount of water vapor in the air. Cold air holds less water vapor before becoming saturated and condensation occurs.
The area’s air with the exhaust is clean because the Environmental Protection Agency and Maricopa County Environmental Services Department have updated standards that demand it.