Daily solar radiation and hourly peak for any location on Earth, calculated from open weather models.
Solar Arc turns raw weather-model output into a plain 7-day solar radiation forecast for any location on Earth. Search a city, or share your position, and you get the total solar energy expected each day in kWh/m² (kilowatt-hours per square metre), the hourly irradiance curve, the day's peak radiation and time, the daily UV index, and sunrise/sunset times — all in one view, with no sign-up required.
The numbers come from Open-Meteo, an open-access weather API built on public national weather models. Because radiation depends heavily on cloud cover, forecasts further out (days 5-7) are indicative and typically firm up as the date gets closer.
Estimate expected generation before installing panels, or check upcoming output for an existing system.
Plan irrigation, spraying windows and crop exposure around expected sunlight and UV levels.
Check peak light hours and UV exposure to plan shoots, hikes, or outdoor shifts.
Get a fast, free read on solar resource availability for any coordinates worldwide.
kWh/m² (kilowatt-hours per square metre) is the total solar energy that falls on one square metre of horizontal surface over a full day. It's the standard unit used to estimate how much energy a solar panel could generate at a given location, before accounting for panel efficiency, tilt and shading.
Forecasts for the next 1-3 days are typically the most reliable, since cloud cover is easier to predict at short range. Days 5-7 are useful for general planning but can shift as models update, so it's worth checking back closer to the date for outdoor or energy-planning decisions.
The UV index measures the strength of sunburn-causing ultraviolet radiation at solar noon. 0-2 is Low, 3-5 Moderate, 6-7 High, 8-10 Very High, and 11+ is Extreme, at which point unprotected skin can burn in minutes.
Solar Arc uses Open-Meteo, an open-access weather API built on national weather models (including ECMWF and GFS). Radiation values are model estimates and can differ from real ground measurements during unusually cloudy or clear conditions.
Solar panel installers and PV system designers use it to estimate expected generation, farmers use it to plan irrigation and crop exposure, photographers use it to plan golden-hour shoots, and outdoor workers use the UV index to plan sun protection.