Pick the right hill for the weather — and your legs.
Hillfinder ranks hills and mountains by how good the forecast is up on the summit, not down in the glen. When a decent weather window opens up, spend it on a hill that's actually worth it instead of guessing.
It takes each summit's grid-point forecast, corrects it up to the real summit height, scores it for the sort of day you're after, and runs it past a few hard safety limits. Right now it covers Scotland's Munros and Corbetts. More regions and hill lists are on the way.
How the ranking works
Weather models flatten the terrain out, so their numbers are for ground that's often hundreds of metres too low. We lift each hourly forecast up to the real summit, where it's usually colder, windier and a lot more likely to be sitting in cloud.
Four things go into the score: wind, rain, how clear the summit is of cloud, and visibility. They're rolled into a 0–10 figure over the 08:00–18:00 window, weighted by whichever profile and season you've picked.
A dangerous day gets pulled from the ranking altogether rather than just knocked down a few points. When that happens you'll see why, along with the forecast value that tripped it, so it's never a mystery.
Decide what a good day looks like
There are three profiles. Each one is drawn as a single bar, and the wider a factor's slice, the more it pulls on the score. Swap profiles whenever you like and the ranking re-sorts straight away. The weighting also changes with the season, which is why every card has a sun/snowflake switch. Flip it to see how a profile leans in winter, when cold turns into a scored cold-comfort factor. Each hill's forecast also shows sunrise, sunset and how much daylight you get, so you can work out your own margin on the short days. I'd like to add an avalanche-hazard gate from the SAIS forecast too, once I've got that feed hooked up.
Sensible default
A sensible default with no single axis dominating - wind, rain and a clear summit carry near-equal weight.
Wind-averse
Minimise the chance of a bad day out. Wind dominates, since it's the condition that most often turns a walk dangerous.
Chase a clear top
Maximise the chance of actually seeing something from the top. A cloud-free summit and long visibility lead.
What goes into a score
You always get to see the numbers behind a score rather than just a verdict. Here's what each one means and how much to trust it.
Wind speed is worked up to the real summit height from the model's own 10 m and 80 m levels, using a logarithmic profile rather than a flat guess. Gusts are shakier ground: there's no reading above 10 m, so I scale them with a rough multiplier that isn't calibrated against station data yet. Take the exact gust figure with a pinch of salt, but it still gets windier and calmer days in the right order.
How much of the top is sitting in cloud, taken from the model's forecast cloud cover at the summit's own altitude and interpolated between the pressure levels either side of the hill's height. Because it looks at cloud where the summit actually is, it can tell real hill fog from a high sky that never touches the top, and it catches cloud sitting on an inversion that a surface-humidity guess would miss. If those levels aren't available it drops back to the older humidity-based estimate, and the forecast page tells you which one it used. It's still modelled cloud, not someone looking out of a window.
Rain probability and amount together, so a brief heavy shower and an all-day drizzle don't just get averaged into the same number.
Forecast horizontal visibility: whether it's a clear day for looking across to the next ridge, or a murky one where you can barely make out the cairn. It counts for most in Views and a fair bit in Balanced.
The summit temperature after wind chill, so a cold top in a strong wind reads as the harsher day it really is. In summer it isn't scored at all (almost every day came out near-perfect and moved nothing), so instead it just drives a hard gate at the dangerous extremes. In winter it's scored directly as a "cold comfort" factor, because a −5°C day and a −18°C day are two very different outings.
The modelled height where the air hits 0°C, from a fixed lapse rate. It's a fair average most of the time, but it can be well out under a winter anticyclone, where the summit ends up warmer than the glen.
Reading the map
Every hill marker is coloured by its score for the day and profile you've chosen, so a good-weather window looks the same wherever it turns up on the map.
The five best hills, without the scrolling.
Next to the map, Top Picks pulls out the five best hills for the day so you don't have to squint at hundreds of markers hunting for the good ones.
Hills close together tend to get near-identical weather, so one good corner of the country could grab all five slots. To stop that, Top Picks only takes one hill per region: five genuinely different days out, spread around the map.
Change the profile, day or gates and the list re-sorts on the spot, always the best five for whatever you've asked for. Tap one to jump to it on the map.
Why some hills vanish
A hard gate isn't a low score, it's an exclusion. A day that fails one drops out of the ranking completely, so a genuinely dangerous day can't sneak through on a good score somewhere else. There are four gates running at the moment, and you can adjust all of them in Settings: raise a limit, widen a range, or switch a gate off entirely.
What it can't do yet
- Gusts are rough. They lean on a crude multiplier that I haven't calibrated against real weather stations yet. Summit wind speed stands on firmer ground; gusts have no upper level to work from.
- Cloud is modelled, not watched. The summit in-cloud figure is the model's forecast cloud at summit height, not a camera pointed at the top, so it's only as good as the forecast. Where the pressure-level data is missing it falls back to a rougher humidity-based estimate.
- The freezing level uses a fixed lapse rate. It can flip under a winter anticyclone, leaving the summit warmer than the valley on exactly the days you care about.
- The walk-in isn't modelled. You get summit conditions, not the approach, and spreading Top Picks around the country is only a rough stand-in for thinking about a real route.
Where the data comes from
Hillfinder doesn't make its own weather or go out surveying hills. It pulls together a few open sources and does the summit-correction and scoring on top of them.
Summits, heights and classifications come from the Database of British and Irish Hills (DoBIH), the community-maintained list that sits behind Munros, Corbetts and the rest.
Hourly forecasts come from Open-Meteo, a free weather API. Each hill's grid-point values then get corrected up to its true summit height before anything is scored.
Base maps are built from OpenStreetMap data, styled with CARTO basemaps and a terrain layer for the main view.
The summit correction, the four-factor score and the safety gates are all Hillfinder's own work. They're deterministic and you can trace every one, so there's no black box deciding what you see.