The weather system definitely glitches out when you restart the game - I had a similar issue during my Adam's Quest playthrough on the mountains! The time it would take for the ice that blocked the ports to melt would reset every single time I saved and quit, so I had to marathon the rest of the tribe's time on the island so we could progress. xD; Since rain is so rare in the burning savanna anyway, I'd imagine you're hitting the same wall!
Gotta agree, though - I'm not a super big fan of the savanna biomes. Even the oasis gets pretty tiring after a while from the lack-of diversity.