A forecast that says heavy rain sounds like one thing, but meteorologists put numbers on it. Wikipedia’s article on rain lists classes by the rate of precipitation, which depends on the time it is measured over. The class names and figures below come from that article as it stood on 2 November 2026; the umbrella notes are our own suggestions, not test results.
The chart
| Class | Rate per hour (as Wikipedia lists it) | What an umbrella does, in our view |
|---|---|---|
| Light | Under 2.5 mm (0.098 in) | Plenty. A compact umbrella is more than enough, and you may not need one for a short walk |
| Moderate | 2.5 to 7.6 mm (0.098 to 0.299 in), or up to 10 mm (0.39 in) by another source | The core job. A good canopy keeps your head and shoulders dry; shoes and trouser hems start to get wet |
| Heavy | Over 7.6 mm (0.30 in), or 10 to 50 mm (0.39 to 1.97 in) by another source | Helps with the top half only. Expect splash from the pavement and a sagging canopy |
| Violent | Over 50 mm (2.0 in) | Shelter is the better plan |
Two sources are cited for the moderate and heavy lines, which is why the chart shows both. If a forecast gives only words, assume the shop or broadcaster has used one of these scales or its own.
How to use it
- Find the hourly figure in your forecast app. Some show millimetres per hour, others a chance of rain and a word.
- Read it against the chart, and then against the wind. Our wind speed chart covers the wind half, because rain at a slant gets round any canopy.
- Decide on the umbrella or something else. For heavy rain, see umbrella or rain jacket; for whether to carry one at all on a given day, see chance of rain.
Size and a quick-open umbrella
Light and moderate rain is where a compact umbrella earns its place, because it is easy to keep in a bag. Calm Eden, which shares an owner with xzvzx, sells the Haven Umbrella, a compact folder: it opens to about 105 cm, folds to 40 cm (15.75 in), weighs about 390 g and opens and closes with one press. Those are the maker’s figures. It is not a wide golf canopy, so for heavy rain with a companion a bigger umbrella makes sense. Calm Eden’s rain umbrella guide goes through what to look for.
In short
- Light rain is under 2.5 mm an hour on Wikipedia’s scale; heavy starts at 7.6 mm or 10 mm depending on the source.
- Read the hourly rate and the wind together.
- Umbrellas do most for light and moderate rain; in heavy or violent rain, plan to shelter or wear a waterproof.
Source: Wikipedia, Rain, intensity section, checked 2 November 2026. Column three of the chart is general advice from us, not a test.
Common questions
What counts as light rain?
Wikipedia's rain article classifies light rain as a precipitation rate of less than 2.5 mm (0.098 in) per hour.
Where does heavy rain start?
Wikipedia gives two sets of figures: heavy rain above 7.6 mm (0.30 in) per hour, or between 10 and 50 mm (0.39 to 1.97 in) per hour. Different sources draw the line in different places, so read the forecast's own wording.
What is violent rain?
The same article lists violent rain as more than 50 mm (2.0 in) per hour. That is a take-cover rate, not an umbrella rate, in our view.
Does a bigger umbrella fix heavy rain?
It keeps more of your upper body dry, but our suggestion is that splash from the ground and wind-driven rain still reach your legs and bag, so plan for wet feet in heavy rain whatever you carry.