Bowcast
Rainbow forecast for Cardiff
Cardiff, Wales, United Kingdom: today's strongest rainbow forecast, the best interval to look up, and the week ahead.
Today's peak · estimated chance
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Checking about 40 forecast ensemble members for sunlit rain near Cardiff…
Sun at your back, facing the retreating rain.
Rainbow weather in Cardiff
Cardiff lives under the North Atlantic conveyor: fast-moving showers with bright spells between them, at a latitude where the sun stays low for much of the day. Low sun means tall bows, and "sunshine and showers" is practically the regional forecast. Spring and autumn, when shower trains are busiest, are the best seasons.
At 51.5° north, Cardiff's useful viewing window shifts with the seasons. Local winter brings longer periods of low sun, while summer usually concentrates the geometry near sunrise and sunset.
Wherever you are, the geometry is the same: a primary rainbow forms opposite the sun while the sun is less than about 42 degrees above the horizon. Bowcast's research-informed heuristics give extra weight to clearing showers. The gauge above applies them to ensemble forecasts to predict the rainbow chance for the 12 km around Cardiff.
The rainbow window through the year
Rainbow questions, answered
- When do rainbows appear in Cardiff?
- Rainbows need sunlit rain with the sun lower than about 42 degrees, so in Cardiff useful windows often occur after sunrise or before sunset on showery days. A study in ZhaoSu, China found that about nine in ten observed rainbows occurred during the hour after rainfall. Bowcast uses that regional finding as research guidance, not a universal rate.
- Where should I look for a rainbow in Cardiff?
- Always directly opposite the sun: put the sun at your back and look toward the retreating rain. In the evening that means looking east; in the morning, west.
- What is today's rainbow forecast in Cardiff?
- Bowcast checks sunlit-rain ingredients around Cardiff, hour by hour, for the next 7 days. When ensemble guidance is available, it shows an Estimated chance from about 40 model members, not a probability calibrated against observed rainbow frequencies. When ensemble guidance is unavailable, it shows a Conditions score /100 instead. This page shows the strongest actionable interval; the Now board shows the interval containing the current time.
- Can you predict a rainbow in Cardiff?
- Not with certainty, but you can forecast the odds. Bowcast works as a rainbow predictor for Cardiff: it reads about 40 ensemble weather members for sunlit rain, checks that the sun sits lower than 42 degrees, and works out which way to face. Read it as an informed estimate of the chance, not a promise that a bow will appear.