How it works

An acclimatised, unclipped adult horse in good condition copes with far more cold than most people expect, and a clipped one with far less. That gap, and the relative weight of rain, wind and clipping, comes from published work: Mejdell and colleagues on horses trained to choose their own rugs, Autio on lower critical temperature, McBride on what owners actually do.

The same research found something more useful than any single figure. Given the choice, the temperature at which horses wanted a rug varied enormously between individuals. There is no one right answer, which is why rugup does not pretend to have one.

A hairy native with a hedge to stand behind and a clipped, lean thoroughbred in an open field are not the same animal on the same night. rugup gives every horse its own temperature to be judged against, built from its coat, how much has been clipped off, its age and condition, any health problems you tell us about, and where it actually stands.

Where it stands is asked twice, once for the day and once for the night, because the two often differ. Indoors is not simply more shelter than a field: a stabled horse is out of the rain and wind entirely, and wants a stable rug rather than a turnout.

A thermometer reading is not what a horse feels. We start from the forecast feels-like temperature, which already accounts for wind chill, then make it worse for the things that strip heat from a horse specifically.

Rain matters most by a wide margin, because a soaked coat loses most of its insulation. A saturated, foggy night does much the same with no rain falling at all. Strong gusts count for more than the steady wind already in the forecast, and count for less if your horse has somewhere to get out of them. A clear sky costs a little more than a cloudy one, since heat radiates away faster.

The day is judged separately from the night, and on its own terms: a rug goes on at the morning check and comes off at the evening one, so the question is what suits the period as a whole rather than any single hour in it.

This is the part that matters most. The morning after, you tap too hot, about right or too cold, and that horse’s number moves. Nothing clever happens behind the scenes: the adjustment is exactly what you told it, it is shown plainly on the horse’s page, and you can reset it at any time.

After a week or two the numbers fit your horse rather than a horse like yours. Published averages get you to a sensible starting point; only you can close the rest of the gap.

Rugs are the winter question. The same forecast answers a few others, and you choose which you want for each yard: frost and ice on the yard, heat and shade in summer, storms worth walking the fence line for, midges for a sweet-itch horse, grass for one prone to laminitis, and ground gone sodden or hard.

Some rest on published work and some are honest rules of thumb. Where we are going on judgement, the app says so rather than dressing it up.

These are starting points drawn from the literature, not a formula with a right answer. The science gives the relative weight of rain, wind and clipping; it does not know your horse, your field, or how it was this morning. rugup is a second opinion to check yourself against, not a replacement for looking at the animal in front of you.

If something looks wrong, it probably is, and telling us so is what makes it right next time.