Back in May we introduced the Weather Visuals suite — interactive, hour-by-hour maps of wind, pressure, temperature, precipitation, cloud and more, built on the same high-resolution forecast data as our summit forecasts. Since then we've shipped two more releases, v2.4.0 and v2.5.0, that take it a lot further: a full synoptic fronts chart, and a dedicated weather map for every region and every one of the UK and Ireland's 11,500+ hills and mountains.
This post covers what's actually in these two releases, with videos of each. There's also a fair bit of engineering behind the scenes that we're genuinely proud of, so we'll link out to a couple of deeper technical posts for anyone who wants to see how it's done.
Explore Weather Visualsv2.4.0 — Synoptic Weather Visuals
The first release brought seven full-country synoptic layers to the app — interactive, real-time maps of the UK and Ireland, up to 72 hours ahead, with a time slider so you can scrub through the whole forecast at a glance:
- Wind — animated wind flow across the landscape, speed and direction hour by hour.
- Precipitation — rain, sleet, snow and thunder plotted by location.
- Pressure — atmospheric pressure gradients with animated isobars.
- Temperature — temperature patterns across the UK and Ireland at a glance.
- Clouds — valley fog to high cirrus, with more accurate cloud weather codes (Mainly Clear, Partly Cloudy, Mostly Cloudy, Mainly Overcast, Hill Cloud, Hazy, Cloud Inversion).
- Freezing Level — where the zero-degree isotherm sits, essential for judging where rain turns to snow.
- Sun and UV — sunshine duration and UV index.
v2.5.0 — Fronts, Regions and Summits
v2.5.0 is the biggest visuals release yet, taking things right down to your own region and your own summit:
- Weather Fronts map — a new synoptic chart showing cold, warm and occluded fronts with isobars and pressure centres, so you can see the bigger picture of what's driving your local forecast.
- Region Weather Visuals — a regional map with 24hr Wind Flow, Precipitation, Temperature, Cloud Cover, Freezing Level, Midge Forecast and a Weather Profile chart, for all 37 mountain regions across the UK, Isle of Man and Republic of Ireland.
- Mountain Weather Visuals — a summit-centred map with the same layers, plus a West-to-East elevation profile and terrain wind map, for any of the 11,500+ hills and mountains we cover.
- Midge Forecast — a seasonal 0–5 midge activity overlay on the Region Weather Visuals page, so you know what you're walking into before you set off.
Weather Fronts
Until this release, the fronts and pressure chart in the app was an image pulled live from the Met Office's newer DataHub service. Functional, but honestly not much to look at — and not something we could style, animate, or line up with the rest of the app.
So Roy built our own front-chart renderer. It runs as a scheduled job on our servers, taking the same 72-hour forecast grid the rest of the app uses, detecting the cold, warm and occluded fronts and isobars directly from the pressure and temperature fields, and drawing the whole chart — coastline, fronts, isobars, pressure centres — from scratch. Every phone gets an already-rendered chart pulled instantly from the edge, rather than waiting on an external image or a render step on your device. We think the result is a lot more attractive than what we were getting before, and it's entirely ours.
For more on how the wider visuals suite renders in real time on your device — GPU heatmaps, the terrain wind view and all — see Why Our New Weather Visualisations Are Built Differently.
Region & Mountain Visuals
This is the one we're most excited about, and it has a bit of history. Regular readers will remember Python Hills, the open-source project Roy wrote about back in May — a few hundred lines of Python that download satellite elevation data (SRTM) and render a shaded-relief terrain image for a mountain, entirely from the command line.
That project has genuinely come into its own for this release. Every region and every one of our 11,500+ summits now has its own beautifully rendered terrain image, generated ahead of time by an extended version of that same pipeline — reprojected to line up exactly with the weather data drawn on top, and paired with a real elevation grid so the wind, precipitation and cloud data you see actually sits at the right height, not just a flat guess. Locations are keyed by coordinate rather than name, since hill names collide and we're not stopping at the UK and Ireland. The whole set — 37 regions and 11,539 summits — comes to around 6.5GB, all baked in advance and served straight from the edge, so it opens instantly rather than waiting on a live map to load.
What started as a neat weekend side-project for generating basic terrain images has turned into the imagery pipeline powering every region and mountain map in the app. Properly impressive work from Roy — go read the original Python Hills post if you want to see where it began.
Explore Region Visuals Explore Mountain VisualsWeather Profile Charts
Sitting alongside the map on both the Region and Mountain pages is a Weather Profile chart — a cross-section through the terrain rather than a view looking down on it. For a region, that's a slice through the area's key peaks; for a mountain, it's a West-to-East elevation profile through the summit itself. Either way you get cloud level and visibility plotted against the actual shape of the ground, over the full 24 hours, so you can see at a glance whether the tops are going to be in cloud and when it's likely to clear.
The mountain version goes a step further with a terrain wind map — wind speed, mean speed and gusts mapped across the terrain as you climb, so you can see whether the wind is going to be steady or lively well before you get up there. It's the same underlying idea we wrote about for the terrain view back in May — see Why Our New Weather Visualisations Are Built Differently — now available for every region and every summit, not just a handful of examples.
Midge Forecast
This one has a nice story behind it. A user emailed us pointing out that we already had all the forecast data needed to predict midge activity — wind, humidity, temperature, cloud cover, all of it — so why not use it? Roy agreed, and had a working midge forecast in the app in under a day.
It's a proper piece of midge biology translated into code, not just a gimmick. Midges are famously weak fliers — anything over about 7mph of wind and they can't get airborne at all, so wind speed carries the heaviest weight in the score, followed by humidity (midges love it muggy), temperature and light levels. Rain knocks activity right down too. The season window only runs mid-April to mid-October, and different regions get a different baseline depending on how much midge-friendly habitat — bog, still water, dense vegetation — they actually have. All of it comes from forecast data the app was already pulling in for every other visual on the page, run through a straightforward weighted score and shown as a 0–5 rating right on the Region Weather Visuals map.
It's a good example of how a lot of these features come about — a user spots that the data is already there, and it turns out to be a genuinely small job to put it in front of you.
Try it yourself
All of this is live now for every region and every mountain we cover. Open any region or summit's forecast page and tap through to its Weather Visuals card, or start from the hub below.
Explore Weather Visuals