Outside temp on dash and clima display rapidly rising today

[hanners]

Hi,

I was stuck in a traffic jam today, when I noticed that digital outside temp on the dash and the temp on the clima suddenly jumped from 19 degrees c to thirty and continued to rise up to about 38 and then started to fall again when I finally managed to get going again. Are either of these linked to the engine coolant. The needle display for coolant isn't working and after a demo from my brother I'll be charging the sensor next weekend. When I drove the car about two hours later it seemed to go up a bit and then back down again, but nowhere near as bad as when I was stuck in the traffic. I've had the car for three years and have never seen this before. The cam belt was changed a couple of months ago and the water pump and coolant were done at the same time. Basically I'm not sure if it's something to do with the outside temp I need to be concerned with or if it's the coolant itself I need to be worried about. I'm going on hols in two weeks driving over to France so just want to be sure things are ok, don't want to be overhearing in traffic in hot weather.

The car is an 03 1.9 tdi diesel

Thanks very much
Mark