March closes the October to March window. The winter lows are still arriving, and the difference from January is that you no longer have to compress a trip into a slot around midday.
That extra light buys you options rather than comfort. Because wind is what ruins a swell here, the useful move is to look at several breaks in a day: Sandvík in the morning, Grindavík when the wind swings, Þorlákshöfn in the afternoon. Three chances beat one good guess. The water has not moved yet and is still at 6°C, so the wetsuit is unchanged, but the snow is off the peninsula roads by the end of the month and the drives that January closes are open again.

