Answer: the ballon will explode.
Step-by-step explanation:
The air in the ballon will increase its temperature and, according to the laws of behavior of the gases, it will expand until it explode.
You can assume ideal gas behavior and use PV = nRT, where you can see that the volume V and P are proportional to the temperature T, so with the increase in temperature the ballon will increase its volume, until the material of the ballon can not expand more, when the pressure will increase and the material will fail.