In his first appearance, he is shown to resist the effects of red sun radiation; however, this radiation was artificial.

The official purpose of the flight was not to gain maximum height, but rather to measure the effect of sun radiation within the tropopause.

The solar machine, using concave mirrors to gather sun radiation strong enough to run an engine.

The polar regions reflect 89-90% of the sun radiation that the earth receives (Stonehouse, 24).

In response, Zod fires the red sun radiation from an Archer rifle at himself, to remove his powers.

Once they have produced a closed canopy, the lack of direct sun radiation at soil makes it difficult for their own seedlings to develop.

Pre-Crisis his ship was hit by yellow sun radiation.

Superman rarely used the Supermobile again after the red sun radiation passed and he regained his powers in the following issue.

The day was remembered due to the red sun radiation in the air and a rainfall of blood.

With the exception of "red sun radiation", which reduces him to a "normal" (or at least vulnerable) level, he has no apparent weaknesses.