You will really stand out and be odd looking and out of place if you make the mistake of wearing the wrong season's dishdasha. A few rules that you can follow to help you out in this dilemma follow:
1) Watch Kuwait TV, I know it has been ages since you last saw it but watch any way. Look at the Kuwaiti news reader, what dishdasha is he wearing ?
2) Look at the people in uniform, especially the police, did they switch to winter uniform?
3) My favorite rule, and one followed by all
4) The most important rule is, if you decide to switch, you cannot go back to your old color. You will experience great shame if you do.
I am still wearing a white summer dishdasha for those who are interessted.