The idea
A week’s forecast tells you what will fall, when the sun will be out and how hard the wind will blow. What you actually want to know is which day to ski. The grade on each resort page is a rule of thumb that turns those forecasts into a single ranking of the days, so that a family choosing between Thursday and Saturday has somewhere to start.
The score is deliberately simple. A day starts at 3 out of 10. Fresh snow adds up to 4, with full marks at 20 cm. The sky over the ski day adds between half a point and 3. Rain, strong gusts and a mild or bitter top-lift temperature take points off. The exact weights are on the methodology page, which is the reference for them; this guide is about how they play out.
Two choices in the scoring are worth knowing about. Snow that fell the day before counts in full, because it is on the slopes when the lifts open, while snow falling during the day itself counts half, because you ski most of it before it has settled. And a rainy day is scored by its rain, not its sky.
One real week: Valle Nevado, 21 to 27 September 2026
This is the upper-mountain forecast for Valle Nevado in Chile, made on the morning of Monday 21 September 2026. It is a spring week with a storm in the middle, which makes it a good test.
| Day | Forecast | Sky | Gusts | Score |
|---|---|---|---|---|
| Mon 21 | Dry | Cloudy | 55 km/h | 2.5 Poor |
| Tue 22 | Dry | Sunny | 44 km/h | 4.5 Fair |
| Wed 23 | Snow, 1–5 cm | Cloudy | 58 km/h | 2.8 Poor |
| Thu 24 | Snow, 1–35 cm | Cloudy | 88 km/h | 2.6 Poor |
| Fri 25 | Snow, 5–15 cm | Cloudy | 73 km/h | 5.5 Fair |
| Sat 26 | Chance of snow, 0–2 cm | Some sun | 58 km/h | 5.2 Fair |
| Sun 27 | Dry | Bluebird | 53 km/h | 5.2 Fair |
Monday had nothing going for it: no fresh snow, cloud, and gusts over 40 km/h, which cost a point. Three for turning up, half a point for the sky, one off for the wind: 2.5.
Tuesday was sunny, which is worth 2.5 points, but still breezy. No snow had fallen. 4.5, and the best day of the first half of the week.
Wednesday brought the first snow, but only 1 to 5 cm, and it fell during the day, so it counted half. Cloud and wind took the rest. 2.8.
Thursday is the interesting one. The models put 1 to 35 cm on it, all three agreeing there would be snow. The grade uses the middle of the range, about 16 cm, and halves it because it falls while you ski, then adds Wednesday’s few centimetres, for around 11 cm of credit and just over two points. But the gusts were forecast at 88 km/h, the top step of the wind penalty, which is three points off, and the sky was cloudy. Score 2.6. On a day like that the upper lifts are likely to be shut, and the grade says so in its own way.
Friday is the best day, and it is worth seeing why. Thursday’s snow, about 16 cm at the middle of the range, is on the slopes when the lifts open and counts in full. Friday’s own 5 to 15 cm adds half of its middle. Together that is about 20 cm, and almost full marks for fresh snow. The sky is still cloudy and the gusts, at 73 km/h, still cost two points. 5.5, which is only Fair, but the best of the week. The page names it the best day to ski, and gives the reason in words: “16 cm the day before and more falling, cloudy, gusts to 73 km/h”.
Saturday had Friday’s snow to ski on, about 8 cm at the middle of the range, some sun and a breeze. 5.2.
Sunday was the bluebird day, worth the full three points for the sky, but the snow was two days old by then and the wind was still up. 5.2, a fraction behind Friday. When two days tie, the earlier one is named.
What the week shows
No day reached Good, and that is the honest answer for a spring week with a windy storm in the middle of it. The grade is not there to sell you a day. It is there to rank them, and it ranked Friday first because it had the most snow underfoot, not because it was pleasant.
The wind penalty did most of the work. Without it, Thursday and Friday would have scored around 5.6 and 7.5. That is deliberate: gusts of 60 to 80 km/h close exposed lifts at most resorts, and a powder day you cannot get up the mountain for is not a powder day.
Notice too that Thursday’s credit rested on the middle of a 1–35 cm range. If the low model was right, Friday’s “16 cm the day before” was really 1 cm, Friday drops to Poor, and the best day becomes Saturday, skiing whatever Friday brought. The guide on why snowfall is a range has more on reading that width. The grade uses the middle because it has to pick something, and the best-day line always shows the range beside it.
Powder then bluebird
The powder then bluebird page uses the same scores to find the days people plan trips around: at least 10 cm at the middle of the range, with two or more models on it, in the one or two days before a Bluebird or Sunny day. Valle Nevado’s Sunday did not qualify that morning. The two days before it, Friday and Saturday, added up to about 8 cm at the middle of the range, under the bar.
What the grade cannot know
The grade is made from the forecast alone. It knows nothing about the base depth, what fell last week, how the pistes were groomed, whether the avalanche control has finished, or whether the wind on the ridge will be worse than the model’s smooth terrain suggests, which it usually is. Today is only graded while at least three hours of the ski day remain.
Use it to decide which day to look at closely, then read the forecast for that day and the resort’s own report before you decide anything.