The weather is relatively the same as normal current texas in terms of how hot and cold it would get. The biggest difference would be the amount of rainfall and precipitation. From my understanding of meteorology if there's more water in the are the higher the chances of rain and since there's an increase in sea level and rivers in the area I think it only goes to show that there would be more rain. Anyway for a swamp biome to exist there needs to be a lot of rainwater. In conclusion same as good ol' Texas, but wetter.

I really should have put this in the setting area. I'll get to that soon.

I just realized that by stating the above the environment outside of the swamp regions will not be desert like it is in current Texas, but more field and mountain like.