overheating

now this one is part of the trip out of austin... going down the highway still in austin (rush hour) around 30mph and maybe 90 degrees outside and i look at the temp guage and notice it at 210 and climbing, it usually never hits 190, but it rose all the way to around 220-225 and stayed there for the next 10 minutes or so then slowly started falling back to normal. my only idea is that the t-stat got stuck open so coolant was too hot to do anything or the t-stat was closed because the coolant was so hot and needed time to cool down, or maybe the t-stat is just going bad, but i haven't ever had this problem before. any ideas?

I would go ahead and replace the t-stat. Are the fans coming on?

yeah i have a new t-stat in the garage and fans come on, was going to install new stat this weekend anyways.