I wake up to a steely cloudless sky above a delicate frost which has thawed by the time I've finished breakfast. It's one of those impressive late-winter mornings when just walking from the shade into the sun is like putting on a woolly jumper.

It is, I think, perfect weather for cutting up a pig - which is lucky because that's precisely what I have planned for the day. I'm hosting one of our 'Pig in a Day' courses. We run them only from November to April, when the weather is reliably cool enough to have a whole pig carcass, in an increasing state of dismemberment (or could that be a decreasing state of memberment?), hanging around all day in the unheated barn in which we host such events, without sweating up or getting worryingly warm. The risk of course is that our guests will become worryingly cold. And so we have one of those giant hair dryer-type blow heaters, with which we occasionally blast hot air at our punters, but not at our pig.

A day like this, when you can warm your back in the sun but not your toes, is obviously preferable, for general hospitality, to wind, sleet and rain. Our guests can wander about the garden in their breaks, enjoying the sharply defined leafless landscape. Such days hint at spring, but they are not yet of it.

But this weather also works in our favour at a more technical level. For example, it makes for better crackling on the roast rolled loin of pork we usually serve at lunchtime. It's all to do with the dryness of the skin when the joint goes in the oven. If you hang the pig up in the sunshine on a day like this, as we sometimes do, the skin will actually begin to tan, turning from flabby white to golden yellow in just an hour or two. And the resulting crackling, scored with a finely adjusted Stanley knife, a good 0.5cm into the fat, but not as far as the flesh itself, then seasoned with flaky salt, black pepper, and coarsely crushed coriander seeds, will be completely sublime.

Precipitative, damp or misty weather not only militates against fine crackling, it also tends to make the outsides of our home-cured salamis a little clammy, as the salt draws the moisture in the air on to the surface where it condenses on the natural (and entirely benign) flush of moulds that live there. This doesn't seriously affect the eating quality of the salami, but it certainly makes it less pleasant to touch. Since we always aim to offer a very tactile experience on our Pig Days, and since this experience informs the expectations of our guests when, at the end of the day, we present them with a tasting platter of our salamis, chorizo, and air-dried ham, there's always a touch of anxiety in the air, when the air in question is on the damp side.

It follows that, if I'm on my way to a Pig in a Day, I'm more relaxed if the weather is clear and fine than if it's wet or foggy. It's not that we don't always have (and I hope give) a great time. It's just that sometimes we have to work a little harder, and sometimes it all flows like freshly rendered lard.

And so I'm setting off in optimistic mood - an optimism which includes distinct visualisations of beautifully blistered golden crackling, of salamis authentically dusted with a bloom of milky-white mould that is pleasingly dry to the touch, and of happy, smiling punters, bonhomously nodding their approval of all that is offered to them, both edible and audible, by myself, our resident butcher Ray, and the very talented River Cottage kitchen team.

But suddenly everything changes. I feel a darkening chill come over the Land Rover. I look out of the window to see that the blanket of blue has, in what seems like mere seconds, become a counterpane of grey. The trees and hedgerow are now bending to a fierce, whipping wind. The windscreen speckles up with a fine drizzle that steadily mounts to become driving rain. The blast of rain becomes a blunderbuss of hail, the size of whose shot turns rapidly from rice to lentils, and then from lentils to peas. The albino frozen pulses come horizontally, and so hard that I find I am driving at walking pace. And it's only five minutes since I left home.

Then the wind drops, the hail stops, the sky's grey brightens a shade, and fat feathery snowflakes come fluttering down instead. They gather pace and density and begin to settle on the ground. I start to contemplate the considerable, mood-elevating compensations of a white winterscape as a backdrop to the day's activities. But the snow goes slushy in mid-thought. And, as it does, so the crackling softens in my mind's eye, and the salamis become distinctly tacky.

The light dusting of snow on the ground has not quite covered the green anyway, and now the green reasserts itself with the help of proper splashy rain. Ahead of me, the sky's brightening, and the rain fizzles out. As I turn into the farm track at HQ, the sun's dazzling in the blue again, and the only clouds left in the sky are fast-retreating flossy wisps of white.

I walk into the barn, where Ray is standing behind his butcher's block, sharpening his boning knife, a whole dead baconer laid out before him.

'Perfect day for cutting up a pig!' he says. OFM