Why did my temperature gauge on my dashboard go over the half way mark today?

What is your question?

I just had my coolant and air conditioning fixed about 3 weeks ago, so I don't think that's the issue. The gauge went a little over halfway and it always rests right under the halfway mark. It only went up once and it was while I was sitting in a drive-thru, after I drove off it went back down and was fine all the way home. I just want to catch something before it is too late. The only other time this happened was about 4 years ago and when my gauge went up the engine started smoking, but all of that has been fixed now. Help a girl out!!! Any suggestions are welcome :)