Big Midgie was built out of a simple frustration: existing midge forecasts cover Scotland in broad strokes, but Shetland has its own conditions, its own season, and its own relationship with Culicoides impunctatus — the Highland biting midge.
Wind is everything up here. On most days it keeps the midgies at bay. But on those rare calm evenings in July, with the sun barely dipping below the horizon and the peat bogs breathing warm damp air — you need to know. And you need to know specifically, not just "moderate risk across northern Scotland."
This forecast is built on a purpose-designed algorithm that accounts for Shetland's unique conditions: the near-24-hour daylight of midsummer, the dominant role of wind and topographic shelter, and the specific habitats — blanket bog, sheltered voes, wooded valleys — that make some locations far worse than others.
The forecast combines real-time weather data from Open-Meteo with a scoring algorithm designed specifically for Culicoides impunctatus behaviour in Shetland conditions. Each factor adds or subtracts points to produce a score out of 12.
| Wind speed | The dominant factor. Midgies cannot fly above ~7 mph. Calm conditions score highest — but topographic shelter means synoptic wind doesn't tell the whole story. |
| Temperature | Peak activity between 12–18°C. Below 10°C or above 22°C, activity drops sharply. |
| Humidity | High humidity and overcast skies favour activity. Midgies desiccate quickly in dry conditions. |
| Light level | Computed from solar elevation angle — not just time of day. In June and July, Shetland's sun barely sets, creating near-continuous low-light conditions that extend active flight time significantly. |
| Rain & UV | Heavy rain and strong UV suppress activity. A bright sunny day is your friend. |
| Habitat | Each location carries a habitat bonus based on terrain — boggy peat moor scores highest, exposed coastline lowest. |
| Season | June and October are weighted lower than peak July–August. Outside June–October, no forecast is issued. |
The algorithm is built on sound entomological principles, but no weather model can replace boots-on-the-ground observation. Every sighting report is stored alongside the actual weather conditions at that moment, building a calibration dataset unique to Shetland.
This matters more than it might seem. Midges are an emerging indicator species for ecological change. Their range is shifting northward. For the first time, Culicoides species in Scotland are being linked to the transmission of disease — a development that was unimaginable a generation ago.
Shetland sits at the northern edge of the biting midge's range. Long-term observational data from here has real scientific value — data that currently doesn't exist in any systematic form.
By reporting what you see, you're contributing to something larger than a forecast app.