The question this answers
Every weather app can tell you whether it rained. That is a different question from whether your garden has had enough, and on the days people actually wonder, the two answers disagree.
A shower that wets the leaves and dries by lunchtime shows up as rain and does nothing for a plant. A downpour after three dry weeks feels decisive and often is not. This site works out how much water reached the roots and how much the plants have used since, and gives you one answer.
How the answer is worked out
Think of the soil as a bucket. Rain fills it, sun and wind empty it, and the size of the bucket depends on how deep the roots go — which is why a pot runs dry in days and a settled shrub can go a fortnight. When the bucket falls far enough below full, it is time to water.
Two things about that are worth knowing. Rain under about 1.5mm is treated as reaching nothing at all: it wets foliage and the soil surface and evaporates. And the water plants lose is not guessed — it comes from the same weather record as the rain, adjusted for what is growing.
The site uses the last month of real weather, not just today, because a garden's condition is the sum of several weeks rather than an event.
What it cannot know
- Snow counts as rain The rainfall figures are precipitation as water equivalent, which includes snow. So a snowy month reads here as a wet one, and a page for a cold place will say "rain" when some of it fell as snow. That matters for the winter months in Canada, the northern United States and mountain towns, and much less for a growing season — which is when anyone asks this question.
- The weather grid is about eleven kilometres across Which is fine on flat ground and less so beside a mountain: a coastal city with high ground behind it shares its square with that high ground, and reads wetter than the city centre really is. Vancouver is the clearest example here. It does not affect the advice — this year and the thirty-year normal are measured the same way, so the comparison is like for like — but the rainfall totals for such a place are the area's, not the street's.
- A town page is about the town, not your garden It is worked out for one point in the town. Your soil, your shade and your planting are all different, and the front page uses your own location instead.
- The starting point is an assumption The sum has to begin somewhere, so it assumes the soil was full a month ago. In ordinary weather that washes out within days, because any real soaking refills the bucket. In a long drought it matters even less, because the soil is simply as dry as it gets.
- It does not know what you did Unless you tell it. The front page has a "watered today" control for exactly that, and what you tell it stays on your device.
The thirty-year records
Each town page compares this year with that town's own normal for the time of year — what it usually gets, the driest that month has ever been, and the wettest. Those come from a complete thirty-year record, 1995 to 2024, for each town.
They are what makes a page worth reading. "Drier than the driest August in thirty years" is a fact about a place, where "unusually dry" is only an adjective.
Millimetres and inches
Rainfall is shown in millimetres, or in inches for visitors in the United States. Whichever you prefer, the control at the foot of every page switches it and remembers.
What the site keeps
There is no account and nothing to sign in to. If you describe your garden or record that you watered, that is kept in your own browser and nowhere else — which also means clearing your browsing data, or switching browser, loses it.
Your location is rounded to about eleven kilometres before it is used for anything, so the site works out an answer for your area rather than for your address.
Where the numbers come from
Weather and the thirty-year records come from Open-Meteo, which draws on national weather services and reanalysis data. Place names come from OpenStreetMap. Both are credited below, as their licences require.