Sandstorm is the most used weather Outside of the Uber tier since it damages all pokemon exept for groung,steel and rock types,pokemon with the sand veil(evassion is boosted in a sandstorm), sand force(power of ground,rock and steel moves are boosted in a sandstorm) or the sand rush(speed is boosted in sandstorm) ability.Sandstorm also raises the sp. def of ground,steel and rock types.
Like with all the other weathers, there are two ways to get a sandstorm on the battlefield. the first is through the sandstream ability witch only hippowdon/hippopatos and tyranitar get both of wich are great pokemon. the other way is through the sandstorm move witch lasts for 5 turns unless the pokemon who used sandstorm is holding a dry stone in which case it lasts for 8 turns. i recomend you use both methods on your team or use both tyranitar and hipowdon. Reuniclus is also very helpfull on a sandstorm team as it has the magic guard ability and can easily knock out fighting types. If you arent using hippowdon then use another ground type. The most commonly used ground type is excadrill since it has either the sand rush or sand force ability making it a power house in a sandstorm. Having a pokemon tht can knock out your opponents ground types is very helpfull. A water type or a grass type do that well.
The counters to a sandstorm team are the same as every other weather team. Eachother. Other weather teams counter sandstorm teams. the most effective one being rain. then hail. Sun teams ussually are not a threat to a sandstorm team exept to the steel type pokemon on yoiur team. Cloud nine and air lock are also effective as they completly stop sandstorm from having any effect at all.