A battlefield you can read is the first job of the art. A battlefield that feels like a place is the second. The weather system is where those two jobs argue with each other.
What it does
Weather, a day-night cycle, rain and fog run as GPU-driven effects on SplinterFaction's GL4 pipeline alongside deferred lighting and instanced healthbars. Every player in a match sees the same sky at the same moment — the effects are driven from shared game state rather than each client's clock, so a night attack is a night attack for everyone.
What it must never do
Hide the game. The rule we hold every effect to is that unit silhouettes and the three bars beside every unit — health, heat, disruption — stay readable under the worst weather the system produces. Fog that made a Loz line disappear would be a mechanic, not a mood, and the game already has a mechanic for that: it's called cloaking, and only one faction gets it.
If it's costing you frames
Disable weather and time-of-day effects first, then lower shadow quality, then turn off non-essential widgets in the widget selector. Deferred rendering means the effects are cheaper than they look, but they're still the first thing to go on integrated graphics — and do check you're actually running on your dedicated GPU, because that's the fix more often than any setting is.