Lowcountry Weather

Because the coast makes its own weather. The land heats faster than the water, the air over it rises, and cooler air off the ocean slides in underneath to replace it. That boundary — the sea breeze front — moves inland through the morning, and where it collides with the breeze coming the other way off the rivers it stacks up enough lift to build thunderstorms. They usually go up twenty or thirty miles inland in the early afternoon and drift back toward the coast, which is why the storm you can see from the beach at three often never reaches it.

No-see-ums are a dawn-and-dusk creature and a still-air creature, and they run in two seasons: roughly April into early June, then again from September into October. The wind is the whole story — above about seven miles an hour they cannot fly, so an exposed beach at four in the afternoon is fine and a marsh boardwalk at seven in the evening is not. They are worst on a warm, windless evening after rain.

A few times a year the sun and moon line up with the moon at its closest, and the tidal range runs a foot or two above normal. On this coast that is enough to push seawater up through the storm drains, so downtown Charleston can flood on a cloudless afternoon with no rain anywhere. It is a spectacle rather than an emergency — it peaks with the tide and drains with it — but it will find the floor of a car parked in the wrong block, so watch where the locals are not parking.

From about the middle of May to the middle of November, yes, and the back half of that is the better half. The sea runs weeks behind the air, so October water is warmer than May water even though October days are cooler. High summer is bath-warm — mid-eighties — which is lovely and is also why the afternoon storms have so much to work with.

Dew point. The air here carries a great deal of water in July and August, which stops sweat evaporating, which is the only cooling mechanism a body has. A dry ninety-five is a hot day; a ninety-five with a seventy-eight dew point is the one that ends beach trips. The number to watch on a forecast is not the temperature but the humidity next to it, and the fix is the same either way: be on the water, or be under an oak, between noon and four.

At the top of this page — the ribbon above the menu turns on by itself when thunder is being reported anywhere between Savannah and Mount Pleasant, and it names the town. It reads hourly observations from the airports rather than a forecast, so it is reporting a storm somebody has seen rather than one a model expects. A storm on this coast is usually something to watch from a porch; the ribbon exists to tell you where to point the porch.