Solar is corellated around time of day on a large scale and cloud cover on a more localized scale. Lack of wind sometimes happens to fairly large regions; interconnections to farther away wind farms helps though.

Weather extremes outside the design can result in outages for all kinds of plants though, so a relatively geographically small and isolated grid like Texas, that has many plants unprepared for cold will likely have outages at plants of all types during a bad cold snap; a particularly bad heat wave might cause issues as well.