1996 Honda Accord driving in the heat or a cooling problem

Engine Cooling problem
1996 Honda Accord 174K miles

I've been having some mild to moderate engine heating issues. It hasn't gotten as high as the red mark on the gauge (yet). It seems to be very similar to what almost anybody can get -- summer, stop-and-go driving -- engine gets hot. But, it seems to be doing it much more often than it should -- instances of 'it' happening don't coicide with heavy traffic/hot day driving.

I drive a '96 Honda Accord that has around 174K miles on it. I had the oil changed at the end of August and the coolant level checked out ok at that time. Should I wait to see if this stops when the weather finally cools down or does this need to be checked out very soon? Thermostat?