Heating up too much

I have a 1993 Grand Cherokee Laredo with the 5.2 L V8 engine. I recently
had the thermostat and the fan clutch replaced, and 1 1/2 years ago the
radiator was replaced.

I live in Utah, and lately it has been getting up to 100 degrees, and I have
found that if I am driving my car around and get stopped at a bunch of stop
light my temperature goes over 210. I am not in rush hour trafic, and am
able to go for a block or two before having to stop. Fortunately, if I can
get going 40 mph or more for a few of minutes the temp goes down to about
190. My only thought would be that the fan clutch that I just had put in
doesn't work right. Does anybody have an idea as to what is going on?