1998 Chevy Corvette Engine running hot

My 1998 corvette convertible has been sitting for about 10 in a garage. It has been -5C or so outside during this time
When I drove it yesterday, it began running at a higher than normal temp, but not in the red zone.
Any thoughts on the cause? IO drove it for about 30 minutes, and it did not overheat, just ran hot.
I use OEM rad fluid and Mobile 1 5-30 synthetic motor oil as prescribed.
Thanks
Mike