資料與計算方式
這一頁說明本站用了哪些資料、降雪量與雪質分數怎麼算出來的，以及這些數字到哪裡為止還可信。每一個數字都是機械產生的，用同一套方法套用在所有地方。
測量的範圍
全球 3,069 座滑雪場的冬季降雪量。其中 397 座在日本，而日本的每一座，我們不只量下多少，也量下的是什麼——下雪時的氣溫、下雪的頻率、改下雨的頻率，以及風。
日本環境省指定的 79 處國民保養溫泉地，也用完全相同的方法測量。溫泉地的清單到處都有；用和滑雪場同一把尺量出來的清單，沒有別的地方有。
重點不是哪一個地方被仔細研究過，而是每一個地方都用同樣的方式量過。 在這裡，能不能互相比較，比單一數值的精確度更要緊。
什麼算是「一座滑雪場」，各地不同。 白馬谷的十座分開計算，因為即使有共通券，每一座也都自己賣一日券。二世谷聯合（比羅夫、Village、Annupuri、HANAZONO）算成一個地方，取代表點測量。志賀高原算成九個獨立經營的區域（例如燒額山、橫手山），再加上一筆涵蓋蓮池周邊較小雪道的項目。這是我們還沒能把同一條規則套用到所有地方的一處，發現一處就改一處。
計算方式
降雪量是十二月到三月逐日降雪量的合計，再取最近十二個完整雪季的平均。南半球的雪場以六月到九月計算。我們從三季擴大到十二季，是因為單獨一個大雪的冬天，會把一座雪場抬到遠高於它長期平均該在的位置。
資料來源是 Open-Meteo 以 ERA5 再分析為基礎的歷史資料——一套計算涵蓋全世界，這也是跨國比較之所以可能的前提。
雪質由四件事構成：下雪時的氣溫、單日超過 5 公分的頻率、下雨的頻率，以及下雪日的風。下多少雪刻意不列入——列進去的話，雪質排行就只是降雪量排行的改寫。
權重與門檻是我們的判斷，不是測量結果。換個人會選得不一樣，順序也會跟著變。這份排行能承載的，是每一個地方都走過同一套計算。
這些數字該怎麼讀
單一雪場的「平年」是平均值，都道府縣或國家的是中位數。 一座雪場的平年降雪量是它各季的平均。都道府縣或國家則取其中雪場的中間值，這樣一個極端的地方就拉不動整體。
比例和絕對值可能指向相反的方向。 北海道從一月到三月流失的雪比全國少，但三月的降雪量卻低於全國中位數。新潟剛好相反：掉得最凶，三月的雪卻仍是全國最多的之一。答案取決於看哪一個時，我們兩個都給。
請讀名次和比較，不要讀公分數。 推估值低於實際觀測，所以這些數字不能拿去和雪場公布的積雪深度或別的網站並列。它們的用途，是比較用同一套方法量出來的地方。
與觀測值的比對
降雪量來自再分析資料——那是推估，不是實際下了多少的紀錄。我們拿它和日本氣象廳 63 個觀測點比對，看差多少。
結果大約是實際觀測值的六成（平均 ×0.60）。它偏低，而且各地偏低的程度不一樣：有些只讀到實際值的三分之一，有些幾乎吻合。
我們試過用固定倍率整體縮放來修正，幾乎沒有幫助，因為誤差因地而異。既然確定修不好，我們就不修正數字，而是把這件事說清楚。
唯一的例外是日本頁面上的地區地圖。 比對附近有日本氣象廳觀測點的 156 座滑雪場後發現，誤差會依地區聚集：北海道約是觀測值的 52%，北陸約 88%。推估是用固定比例把降水換算成雪，所以在雪更乾的地方會低估得更多。
我們發現並訂正過的錯誤
本站的數字，是靠找出錯誤並訂正而建立起來的。每次修正，我們都把「哪裡錯了、怎麼修的」記在這裡。結論因此改變的文章已經重寫，並附上說明。以下紀錄維持英文原文，以免改寫了歷史本身。
August 2026Switching to a finer weather model would have made things worse
A reader told us some resorts were ranked implausibly. We considered moving to the Japan Meteorological Agency's finer 5 km model, but first checked both against measurements at nine weather stations. The current model came to 73% of what was observed on average; the 5 km model came to 42%, and fell below half at every station. Switching would have made the figures worse, so we kept the current model. The reader was right, though: the error differs from place to place, and that is what was upsetting the ranks. The verification above began with this.
September 2026The snow-quality ranking mixed in places that had not been fully measured
Of the 454 places scored for snow quality, 81 did not have all three seasons of data — the download had hit a limit and stopped partway. Ranking places measured over different numbers of seasons in one table distorts the order, so every place was re-measured over three seasons. 393 places moved, and the tables and text of 12 articles were corrected one by one (Tengendai went from 3rd to 9th, and its headline changed with it). Any place missing a season is now always listed by name before anything is published.
September 2026Month-by-month patterns were built from three seasons
For a ranking of season totals, three seasons are enough: every place shares the same three winters, so their quirks fall on all places alike and the order barely moves. The shape of a season is different. A question like "is December or January snowier?" can flip for a whole region because of one unusual winter. Re-measured over 11–12 seasons, March snowfall at resorts above 1,200 m was 60% of January, not 91%, and "Kusatsu and Nikko Yumoto get the most snow in March" was wrong — both peak in January. One article was rewritten from its conclusion down, and two comparing Japan with the Alps and North America were withdrawn. Those two were later re-measured over the same number of seasons; neither conclusion held, so one was rewritten with its new finding and the other stays withdrawn.
September 2026Year-to-year variability was compared over three winters
The three winters we were using (2023/24 to 2025/26) did not include 2015/16 or 2019/20, the worst winters at most resorts. Over twelve winters, the swing at Kiroro — which we had called the most stable — is 70%, not 9%, almost the same as Hakuba's 74%. Iwate went from the most stable prefecture to one of the least. Bad winters arrive across the whole country at once: 240 of 377 resorts had their worst winter in 2015/16. Picking a stable region to dodge a bad winter is not something you can actually do, so the article was rewritten around how much snow is left in a bad winter. Eight other affected articles carry a correction note and are being rewritten in turn.
September 2026World ranks quoted in articles had gone stale
Each time resorts are added, world ranks shift slightly. We did check the ranks quoted in articles against the data, but it turned out the check had been passing without comparing against anything. Once it was fixed, it found 16 outdated ranks, which have been corrected. A rank in an article that no longer matches the data now gets flagged.
這些數字說不出來的事
我們不做預報。 這裡公開的是過去的觀測與計算，加上氣象資料供應商提供的當日資訊。我們不製作自己的預報。
雪場公布的積雪深度是完全不同的東西。 每一家在自己的地點、用自己的方式測量，所以那些數字彼此之間並不可比。我們的數字之所以可比，只是因為每一個地點都走過同一套流程。
聯絡
關於計算方式的問題、資料使用的洽詢、刊載內容的訂正要求，請由聯絡頁面告訴我們。