What "Tank Rain" Means in Bermuda
Bermudians use "tank rain" to describe rainfall heavy enough to meaningfully refill a household cistern. Not every shower counts — it takes sustained, moderate-to-heavy rain to move the needle on a 10,000–20,000 gallon tank. A light drizzle that dries off the pavement in minutes does nothing for your supply. Growing up in Bermuda, rain was never something to complain about — it was a joyous occasion. When the sky darkened and the heavy drops started hammering the roof, you knew the tank was filling. That sound meant security.
The distinction matters in a way most weather apps never account for. Knowing the probability of rain is useful. Knowing whether that rain will actually fill your tank is essential. Bermuda has no natural freshwater supply — every household depends on rain collected through its roof catchment system.
What Makes a Storm "Tank Rain"
The tank refill formula — gallons = rainfall (inches) × roof area (sq ft) × 0.623 — puts numbers to the feeling. A typical 1,500 sq ft home collects roughly 935 gallons per inch of rain. On a 10,000 gallon tank, that's a 9% refill. Half an inch barely registers. Two inches is a proper tank rain event. That's why Bermudians track rainfall totals, not just probability — the amount matters as much as whether it rains at all.
The Tank Rain Scale on the homepage translates raw totals into practical labels: from Light Shower (negligible impact) through Good Tank Rain to Big Tank Refill (over 1 inch). Thresholds are calibrated to typical Bermuda tank sizes.
How Tankrain BDA Tracks This
The rainfall page shows today's precipitation, a 7-day forecast, and the Tank Rain Scale. The tank calculator lets you enter your roof size and tank capacity to see exactly how much a forecast event will add to your supply. Check it before a storm, not after — that's when the information is useful.
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Check the current forecast and see how much rain your tank could collect this week.
View the Forecast