By Weather Malta · Published 31 October 2026 · Updated
A forecast of 0.1 mm can look surprising after a shower. Before comparing the number with what happened outside, check the location, the time window and whether it is a forecast for the remaining hours. Rain amount, how hard it rains and the chance of rain answer different questions.
What does a millimetre of rain mean?
Rainfall in millimetres measures the accumulated depth of water over an area. One millimetre equals one litre of water per square metre. The same amount can arrive slowly or in a short burst: 1 mm spread over a day and 1 mm falling in five minutes have the same total, but feel very different.
| Forecast wording | How to read it |
|---|---|
| 0.1 mm / 1h | A total of 0.1 mm forecast over that one-hour interval. |
| Rain total: 0.3 mm · 12:00–18:00 | A total of 0.3 mm over the afternoon, not 0.3 mm every hour. |
| 0.3 mm for the rest of today | Only the remaining forecast hours. Rain that fell earlier is not included. |
| Rain on the map: 0.3 mm / 6h | A total of 0.3 mm over the six-hour window shown for the selected location. |
Daily rainfall categories used on Weather.mt
For complete 24-hour location forecasts, Weather.mt uses the India Meteorological Department's daily accumulation categories below. These describe the total amount expected over 24 hours. They are a reading aid, not a Maltese warning scale or a statement about the intensity of each shower.
| Daily category | Forecast total over 24 hours |
|---|---|
| No rain forecast | 0.0 mm |
| Very light rain | 0.1–2.4 mm |
| Light rain | 2.5–15.5 mm |
| Moderate rain | 15.6–64.4 mm |
| Heavy rain | 64.5–115.5 mm |
| Very heavy rain | 115.6–204.4 mm |
| Extremely heavy rain | 204.5 mm or more |
IMD includes trace rainfall in its lowest category. Our numerical labels use totals rounded to 0.1 mm. A displayed zero means no rain in the model's reported amount; it does not guarantee that no drops will fall. Daily category labels appear only when all 24 hours are covered. We do not assign them to remaining-day totals, incomplete data, regional averages or the 23- and 25-hour local days when the clocks change.
Why do different guides use different thresholds?
There is no single numerical scale shared by all these services. Bhutan's National Centre for Hydrology and Meteorology defines very light daily rain as 0.1–0.9 mm, while IMD's daily category extends to 2.4 mm. Both describe daily accumulation. Weather.mt names its chosen source so the label has a clear meaning; changing scales would change the description, not the forecast millimetres.
Rain intensity: how hard is it raining?
Intensity is a rate, usually expressed in millimetres per hour. Canada's Manual of Surface Weather Observation Standards defines light rain as 2.5 mm/h or less, moderate rain as 2.6–7.5 mm/h and heavy rain as 7.6 mm/h or more. The US National Weather Service uses similar thresholds in inches per hour for its ASOS present-weather sensor. These are intensity classifications, not daily-total categories.
An hourly forecast total is still an accumulation over an hour. Dividing a six-hour total by six gives an average rate across that whole interval, including any dry spells; it cannot tell us the peak intensity during a shower. A small daily total can therefore include a brief downpour.
- Environment and Climate Change Canada: MANOBS, section 6.6.2.5.2
- US National Weather Service: ASOS rain-intensity thresholds
Weather symbols and rain amounts can tell different parts of the story
A period or day summary uses the most frequent weather symbol, so mostly clear conditions can appear alongside a non-zero rain total. Check the hourly symbols and rain intervals to find the shower hours. A daily accumulation category is a separate description of the total.
Weather symbols describe conditions over a time interval. The UK Met Office explains that showers can happen between the times displayed in a forecast. Read the weather description alongside its time window, rainfall amount and chance of rain.
Rain probability is a separate forecast
A percentage describes the chance of precipitation during its stated interval; millimetres describe the forecast amount. You cannot convert 0.1 mm into a rain probability. Weather.mt shows a probability only when the provider supplies it. An unavailable probability does not mean a zero chance of rain.
Read the location and time window first
- Regional rain descriptions summarise conditions across the islands. Choose a location forecast or the map for local rainfall amounts.
- Today covers the remaining forecast hours, beginning with the current clock hour. It is not a measured total since midnight. A number can decrease as earlier hours pass or the provider updates its forecast.
- The ≈ sign marks a period total estimated by spreading a longer provider interval evenly across a time boundary. It does not tell us exactly when the rain will fall.
- A missing total means the interval coverage is incomplete. It is not a prediction of dry weather.
- Forecast timestamps use Malta local time. The issue time shows when the provider produced the forecast; the interval shows when the predicted weather applies.
Why might it rain more than forecast?
Weather models describe an area rather than every street. ECMWF explains that average precipitation over a model grid cell can be low even when individual showers are heavy. A shower's timing and position can also differ from the forecast. To assess an event, compare a forecast issued before it with a local rain-gauge measurement over the same interval. Weather.mt's archive contains saved forecasts, not measured rainfall.
- ECMWF: limitations when forecasting convective precipitation
- Compare local forecasts
- Weather in Mosta
- Malta and Gozo weather questions
Put the guide in context: local weather questions answered · explore the weather archive.