i had a similar problem. the temp sensor under the car got loose. in my case, it was hanging near the ground so i got temp reads of 110-120. the dealer was able to reattach it.
The sensor is located in a small plastic clip attached to the wire mesh panel in the front bumper, on the far right side. It is barely visible but you should be able to see it if you look closely. It is on a wire and in your case it may have worked itself loose. It should be easy to re-attach it. It might be flopping around, coming in contct with the radiator.
Mine started doing that almost immediately after delivery. Had it fixed at the 3000 mile service and a couple days later it was doing it again. Glad to know where it is so I can slip it back in...the next service is a long ways off. It's definitely not 140 degrees F in Houston, but my dashboard tells me it is.
(It is 140F in October, of course, but now it's late November.)