Working with our weather data provider MeteoGroup, we provide hourly forecasts out to 14 days. Why does the detail keep changing on the hourly forecast? Of course, the perception of temperature is rather subjective, so these should only be taken as broad guidelines. Thus, the "feels like" temperature is designed to give an indication as to when these extra factors may combine to make the apparent temperature seem higher, or lower, than indicated. Similarly, but going the other way, a windy and dry day, especially when cold, may lead to the air "feeling" colder than the temperature may suggest. Thus, the air may "feel" somewhat warmer than the temperature indicates.
In light winds and high humidity, especially with higher temperatures, any moisture on our skin will be slow to evaporate, and so the cooling will be lower. Our perception of temperature comes down to how quickly (or not) our skin is cooled. The two main factors which cause this sensation are wind speed and humidity. However, there are factors which can lead to a day feeling hotter or colder than this value alone might suggest. The temperatures in our forecasts represent the "air temperature" forecast - that is, the temperature that a properly shielded thermometer would record. When it occurs, it can be a strong short downpour and therefore the predicted amount of precipitation is reasonable high to generate a "wet" weather symbol - despite a relatively low precipitation probability. On the other hand, in shower situations the chance of rain in an individual hour might be low - in particular as it is difficult to predict long time ahead at which particular time an isolated shower will hit a particular place. a cloud) but the probability of rain might be quite high. In this case, the weather symbol would remain as a "dry" weather symbol (e.g. This would be the type of weather where you feel a few spots of rain on the breeze, but it's not even enough to dampen the roads and pavements. This means that where very light, patchy rain or drizzle is expected, there may be occasions where the chance of seeing at least a few spots of rain is high (so a high % chance of rain), but the actual amount expected is very low (less than 0.1mm of rain in one hour). In order to generate a wet weather symbol, there needs to be at least some measurable rainfall expected (over 0.1mm per hour, say) and a reasonable chance of rainfall. For "wet weather" symbols these measurements include the hourly rainfall amount as well as the % chance of rain (probability of precipitation). The weather symbol is generated by taking a number of weather measurements, and then working out the most likely weather type based on them. How does % chance of precipitation relate to the weather symbol? Note that when the chance of precipitation is less than 5% it will appear grey on the website. This gives you the chance to spot when, for example, a shower may be approaching your location, as the probabilities will tend to rise. As MeteoGroup forecasts take advantage of hourly updates, which include real-time information from radar, satellite, and nearby weather station observations, you may notice the probabilities changing in the short-term (next 2-3 hours). The probabilities are given for the location chosen, and thus are valid for that location only. In a nutshell, it means that, whilst you may get some rain, it's much more likely (but not certain) to stay dry.
So what does a 20% chance of rain actually mean? It means that out of 100 situations with similar weather, it should rain on 20 of those, and not rain on 80. Our data supplier MeteoGroup uses the probability of precipitation (% chance), and this ranges from 0% (no chance at all) to 100% (it will be wet).
What does % chance of precipitation (rain, snow, hail, etc) mean? This video offers further detail: Why are showers so hard to forecast? If you are making plans and spot a showers symbol on our website or app, you may find it helpful to review the latest video forecast for more in-depth information from our team of meteorologists.
We flag this up on the TV and video forecasts where we can give more context, and in the text on the website. It is also possible for showers to form into bands which can cause one area to have continuous rain. Showers (including hail/thunder/snow) can be very heavy or long lasting. Their time or location doesn't have to be far out for the forecast not to be 100% correct. Showers can be especially hard to forecast. Questions about weather forecasting informationĪ short spell of rain or showers has been forecast.