Is this also with night mode? Have you enabled shaders and did you try with different settings? Have you modded gtasa files?
This problem is not related to server, nobody else has this bug.
Have you installed latest GPU drivers? Reinstall GTA:SA and MTA:SA and make sure it's fresh, clear installation, not modded one (most pirated version are modded which can cause many weird bugs, don't use them).
Also try different video settings.