MacBook Air fan running loudly even though 90% idle CPU

My fan is constantly running at what seems like full-speed for a majority of the time I have my computer turned on. I typically only have a couple applications running – Chrome, Photoshop (with 1 small file at a time), Messages, and Spotify.

Activity monitor CPU (All Processes) shows 80-90% idle CPU, the the occasional spike when I started up a new application. Even when I have 90% idle CPU, the fan is still running very loudly.

I have already tried an SMC reset (per this article Intel-based Macs: Resetting the System Management Controller (SMC) - Apple Support) but it didn't help.

Any ideas?

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MacBook Air, 13-inch, mid 2012

Processor 1.8 GHz Intel Core i5

Memory 8 GB 1600 MHz DDR3

Storage19 GB free out of 120GB

Graphics Intel HD Graphics 4000 1024 MB

Software OS X 10.9.5 (13F34)