Well, it;s getting hotter out, so even that can make a difference. If it stays there, just let it be, no issue. You can easily raise the idle just a bit with the screw on the throttle body. I know a couple people that have lower temp thermostates in thier SC Camry/Solara, and no one has any bad issues. Nothing to worry about unless it gets worse.
Thanks...
When it's running cooler (than normal) at a stop, it's around 650RPM...as the temp rises back to *normal* with further stop and go (mostly heavy traffic), the idle RPMS RISE back to range of 690. I also noticed that the temps run a tad LOWER with AC ON (in stop and go). This is probably to to higher RPM (than when off) which turns the WATER PUMP faster. All in all, I'm impressed with the way the temps stay down with the 160 when car is moving..even at 25 MPH in hotter weather.