A weather seal that inserts into a gap between glazing panels has an H-shape with a snap-on female receiver at either end for receiving a tongue extending from a structure at one end and a cap tongue in the other. A web extending between a pair of walls provides a weather barrier and allows the walls to flex enabling the snap-on action. A pair of sealing fins and a pair of bulbs extend laterally from the H-shape, bridging the gap to exclude weather infiltration. The second receiver is covered by extensions joined at a slit permitting the weather seal to be used without a cap. Alternatively, the cap may be affixed to the weather seal by pushing a cap tongue through the slit and into engagement with the second receiver.