For best performance, skylights should consist of two layers, with one of them consisting of tempered glass (for improved resistance to larger embers striking and breaking the glass). Likely exposure for a skylight would be from the impact of an ember or other object lofted during a wildfire.
The upper (domed) light in the photograph above is plastic, and won’t be able to withstand an A brand exposure. To prevent entry of burning embers during a wildfire, this operable venting skylight should be closed.
For more information about skylights, see http://firecenter.berkeley.edu/bwmg/roof-3.html.