Every fall, skiers in the Northeast watch the forecast for one thing: the first night cold enough for resorts to fire up the snow guns. The thermometer doesn't really answer that. So we built Can They Make Snow?, a free site that checks whether a ski resort can make snow right now, and when it next can.
The number that matters is wet-bulb, not air temperature
Snow guns spray fine water droplets into the air, and the snow they make depends on those droplets freezing before they land. That depends on the wet-bulb temperature: how cold the air gets as water evaporates into it. It combines temperature and humidity, so dry air at 32°F can work while damp air at 30°F can't.
Snowmakers can usually start around a 28°F wet-bulb, make good snow below about 25°F, and do their best work below about 19°F. Those are the thresholds the site uses to give each resort a plain YES or NO.
Where the data comes from
The site uses the National Weather Service's free forecast API (api.weather.gov). For each resort we pull NOAA's hourly forecast for that spot, work out the wet-bulb for every hour of the next two days using Stull's 2011 formula, and look for the next window that's cold enough. Each resort page shows:
- a live YES or NO at the base and at the summit
- when the next snowmaking window opens, how long it lasts and how cold it gets
- a 48-hour wet-bulb chart
- expected new snow and a 7-day outlook
The base and the summit can disagree
A mountain isn't one temperature. Air usually cools with height, so the summit can often make snow before the base. On calm, clear nights it can flip: cold air drains into the valley and the base ends up colder than the top.
So we check both. When the summit sits in its own NOAA forecast grid cell, we use NOAA's forecast for it. When it shares a cell with the base, we estimate it from the base forecast using standard cooling rates by elevation, and label it as an estimate.
Alerts, so you don't have to keep checking
You can follow a resort and get an email when a snowmaking window opens, or when a storm is set to drop 3, 6 or 12 inches in the next 48 hours. The site checks every hour, sends one combined email per check, and stays quiet overnight in the resort's time zone.
How it's built
Can They Make Snow? runs on October CMS and Laravel, the same stack behind a lot of our client work. A few details we liked building:
- NOAA responses are cached, so a busy morning doesn't hammer their API.
- Every lookup gets its own share image, so a link posted in a group chat shows the answer.
- Each of the 119 resorts has its own page, listed by state, so people can find their mountain straight from search.
It's a side project, but it's the kind of thing we like doing: take a public data source, do the math properly, and turn it into an answer you can read in five seconds.
Check your mountain at cantheymakesnow.com. It covers 119 US resorts, and any US town or address works too. It's free, with no ads and no sign-up.
Got a public or internal dataset that should be easier to use? Talk to us.