Thanks for your comments. All your points are valid.
I didn't consider slowing down the player when reloading, however as the waves progress the zombies get faster, have more health and there are more of them. It is an unwinnable game so eventually you will be overwhelmed.
The weather is random, so you could have a dark night time if the weather is bad, which would cause low moon light. I should have added a point light to the player and tweaked the weather settings a bit.
The weather system already had ambient sounds. I didn't have the music/assets or the time to put together an adaptive music system.
Thanks for your suggestions!