March is the last full month of the north-east monsoon on the south coast. The swell is the same one that ran all winter and the mornings are still offshore, but the wind starts to arrive earlier in the day. In a week, count on four days out of seven at Plantations in Midigama and three in Weligama bay. The days that go are blown out, not flat: a third of the month at Plantations, twice January's share.
The sea climbs to 29°C, and March into April is the hottest stretch of the year on land too. That changes how long you stay in. A session ends when your arms are done, not when you start shivering, so a long morning in the water is realistic as long as you are out of the sun by late morning.
Plan the day around the wind. Be in the water soon after sunrise, when it is cleanest, rest through the middle of the day, and treat the late session as a bonus rather than a certainty. From April the offshore becomes a dawn affair and the season starts to close.
It is still high season, so rooms cost what they cost in February and the camps fill. For the waves, base yourself at Ahangama or Midigama, a few minutes apart: The Rock off Kabalana beach is a both-ways reef peak that works at any tide, and Midigama has four reefs across two kilometres. For a first week, Weligama and its sand remain the place. If a morning is blown out on the open coast, Hiriketiya is the fallback, about an hour east of Weligama: its two headlands wrap the swell into the cove and keep a wave when the beaches close out, and the village is lanes, flip-flops and early nights. Take the first half of March if you can: the wind gains ground as the month goes on.

