Rainbow forecast for San José
San José, Costa Rica: today's peak estimated rainbow chance, the best forecast interval to look up, and the week ahead.
Rainbow weather in San José
San José runs on convective rhythm: heat builds cumulus through the day, showers collapse out of them, and the sun returns fast. That quick alternation of downpour and sunshine, especially in the wet season, produces frequent late-afternoon bows once the sun drops below 42 degrees.
At 9.9° north, San José's midday sun often climbs above the geometry for a visible primary bow. Early morning and late afternoon are the most dependable viewing windows through much of the year.
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 for the 12 km around San José.
Rainbow questions, answered
- When do rainbows appear in San José?
- Rainbows need sunlit rain with the sun lower than about 42 degrees, so in San José 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 San José?
- 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 the estimated rainbow chance in San José today?
- Bowcast checks about 40 forecast ensemble members for sunlit-rain ingredients around San José, hour by hour, for the next 7 days. The result is an estimated chance from model agreement, not a probability calibrated against observed rainbow frequencies. This page shows today's peak and best forecast interval; the Now board shows the interval containing the current time.
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