From Universe Wars

With advanced research you will eventually be able to create a Weather Control System, which will help even out your weather. With a WCS watching over your empire, you will not suffer the ill effects of extreme weather, but you can still achieve all bonuses from nice extreme weather.

While a WCS will not guarantee that you'll never see a storm (for what healthy empire has no storms?), it will increase the odds of nice weather.

Watch out, however, for your WCS may be a target for your enemy, or you may choose to take out an enemy's WCS. If this happens, the target will likely experience an extreme condition.