Pic says it all .
There's partial to total blockage of the tubes in the middle, the hot coolant is doing it's best to pass whatever coolant it can down thru the few tubes on the sides. If you drag your knuckles across the rad, the center tubes would be cool compared to the outer tubes.
Looking at the pic, you can see why I have always asked for temps from the actual rad fittings, not the hose, see the temp difference of the hose, cooler, false temp.
Get the rad rodded out .
The cooling system should have the capacity to keep coolant at thermostat temp, if it can't, and it goes higher, something is deficient, you are beyond capacity to keep it at thermostat temp, and any " work" will cause overheating.
Ideally your thermostat is never totally open at operating temp, it modulates, and needs to be able to open further when "work" causes the engine to create more heat, - or temp will continue to rise till it pukes .
Sorry OP .
Good luck