The weather, which looks like a single phenomenon, is in fact a set of different meteorological events expressed in specific values (numbers) at a particular point in space at a particular time.
These phenomena are also called weather elements or parameters or parts, and the like. You already know what those parts are: temperature, precipitation, wind, and more. However, even if these three words seem familiar to you, it is good to understand the other elements that you may not even know about. They could be useful to you, in particular, for doing various sports and outdoor activities.
In this guide, we will deal with all the main weather elements. They can be divided into several groups: basic parameters, additional parts, and various kinds of indices and optical phenomena — don't worry, there are no more than 10–12 of them in total.
Weather conditions are the first thing you usually pay attention to when you look at the general weather forecast for the day. There are several dozen of them in total, but they are conveyed in simple words that anyone can understand: sunny, overcast, rainy, windy, and so on.
Many people limit themselves to this weather element when they read the weather forecast without taking into account more accurate data on precipitation, wind, clouds, and other parameters. I think they should. That's what this whole guide is about.
Anyway, in the forecasts, these conditions are indicated by weather symbols most of which are also easy to undestand from the first try: the sun is for sunny, two raindrops are for moderate rain, the cloud is for a cloudy day...
Every weather forecast contains the three main weather parameters that we have already outlined above: temperature, precipitation, and wind. These elements make up the weather in the first place because they are the most critical for humans: our feelings of warmth and cold (and clothing choices) are directly related to temperature; when it rains, we find it difficult and simply less comfortable to do various activities, including a casual walk around town; wind also affects how we feel as it interacts with temperature and precipitation.
When we talk about temperature, we mean air temperature, which can be different depending on the time of year, altitude, and other factors.
But there is a second common type of it that you can see in the weather forecast — feels like temperature. This is our real sense of air temperature, which may seem higher or lower depending on the humidity or wind. That's why two important parameters are taken into account when calculating this temperature: the Heat Index and the Wind Chill.
Both temperatures are measured in degrees, in the two common systems of Celsius and Fahrenheit (1 °C is 33.8 °F), and come in daytime and nighttime temperatures, and the lowest and highest during the day, and the average.
Precipitation is atmospheric moisture that falls to the ground in the form of rain, snow, or hail. But it can also be drizzle, sleet, and many other types of precipitation. They result from interactions with other weather elements: temperature, humidity, wind, and others.
Sometimes the precipitation forecast is also expressed as a percentage. In this case you may see the phrase "Chance of rain" in the forecast. This seems simple to understand, but in general, calculating the probability of precipitation is a complicated thing, which has recently been actively debated on social networks.
Usually, the rain is measured in millimeters (mm) the snow is measured in centimeters (cm), and other units common to your region: inches (in), and so on. In general, heavy rain is 15–50 mm (0.5—1.9 in) in 12 hours, heavy snowfall is 7–20 cm (2.7–7.4 in) in the same 12 hours.
There are two main characteristics of wind that are not difficult to guess (or to find out if you often check the weather forecast) — speed and direction. They determine how fast the wind is (i.e. strong and destructive) and where it blows — or rather, FROM, because that’s what it means: north (N), southwest (SW), or north-northeast (NNE).
But that’s not all you can know about wind, of course, because it’s probably the most interesting weather parameter. For example, there are many different types of wind, including the wind gusts; it is measured with different scales and can be represented by the wind barbs on the weather map; you can read it better and faster with a wind rose, and more.
If we talk about the exact units of measurement, they are also the units adopted in your region: meters per second (m/s), miles per hour (mph), and others.
Greg Rosenke / Unsplash
In addition to the three basic parameters mentioned above, there are usually three other weather elements that are also considered essential: atmospheric pressure, humidity, and visibility. Their essence is not difficult to guess from their names.
In simple terms, atmospheric pressure is the weight of the air, or its pressure on the surface of the earth and everything on it, including humans, animals, plants, rocks, and other living things. Hence, pressure is either high or low.
The most important thing to know about changes in pressure is that it helps to predict the weather, such as weather fronts, which will be discussed later. In particular, if you know exact atmospheric pressure figures, you can predict the weather for the next 12–24 hours. The pressure also affects how people feel, and so on.
Pressure is measured in millimeters of mercury (mmHg), inches of mercury (inHg), or hectopascals (hPa) at sea level (in a normal weather forecast), but it can also be measured at different altitudes, because the higher you are, the less air above you and its pressure on you. The normal pressure is 760 mmHg (29.92 inHg, 1,013.25 hPa).
Figuring out humidity is as easy as figuring out air temperature. It is characterized by the degree of concentration of water vapor that is contained in the air. In other words, the air can be wetter or drier depending on temperature and atmospheric pressure. Humidity also indicates the likelihood of precipitation or dew point or phenomena such as fog.
Humidity, however, is more complicated than it sounds. That’s because there are three different subtypes: absolute humidity, relative humidity, and specific humidity. The humidity you see in the weather forecast is the second type, although all three are widely used in meteorology and are related to each other.
The relative humidity is measured in percentages (%). Without going into too much detail: the higher the percentage, the more humid the air; the less, the drier the air. Both are more difficult for a person to breathe and feel on their skin than air with average, comfortable values of humidity.
Visibility as a weather element speaks to the degree of atmospheric transparency, that is, whether we see some object at a distance or not. For example, the most common fog is a serious obstacle for drivers, cyclists, and even pedestrians. Other weather elements that reduce visibility are haze, snowstorms, sand or dust storms, and others. That’s why visibility is one of the crucial parameters, which is included in almost all forecasts as one of the top ten things.
This weather element is also divided into several types — primarily depending on the time of day, and refers to the actual weather, that is, what is observed here and now (and will not be tomorrow).
Visibility is measured in the same units as the distance at which the observed object becomes invisible to the eye and is expressed in kilometers (km), miles (mi), and other units.
Among the weather elements in the weather forecasts, you are also likely to see one or more indices. These are the same units of measurement as kilometers or inches, but for those phenomena that cannot be measured any other way.
Usually indices are simple scales consisting of numbers and a color designation. Generally speaking, the lower the index (0, 1, 2...) and the cooler the color (green, blue... vs. orange, red and purple), the smaller and better the index. But NOT always.
There are two main weather indices that you can find in almost all weather forecasts:
The UV Index is an index developed and standardized for use around the world by the World Health Organization (WHO) and several other such agencies to measure the level of ultraviolet radiation from the sun. It is bad for our skin and our general well-being. Don’t panic. In small quantities, it is considered even useful because, without the sun, there would be no life on Earth. But if you are in direct sunlight all day, you can get a sunburn, as you know yourself. That’s what this index is about, in a nutshell.
AI Index is an index for measuring the quality of the air. In other words, we can use the index to determine how polluted the air is in a particular area: it could be the place of your living, your favorite outdoor spot, or your travel destination. Unlike the UV Index, there is no single system for measuring air quality, so different countries use their own systems. Nevertheless, they are generally similar. Use the one used in your country.
Meteorology is not only temperature, precipitation, and wind, but also the various optical phenomena that can be observed in the atmosphere, that is, essentially how light behaves in relation to the observer on Earth. Weather forecasts usually indicate the main such a phenomenon — sunrise and sunset, and sometimes the length of daylight hours.
The length of daylight hours can be important, for example, for hikers to know how much time he or she has to walk a certain distance to a hut or set up camp before dark. This is critical in the outdoors because there is no lighting like in the city, of course. In any case, you need to have your own source of light: a lantern, a torch...
Along with the sun, the rising and setting of the moon, as well as the phases of the moon, can be very useful, because it is the only natural source of light at night. In my experience, moonlight provides enough illumination to navigate the terrain.
At the time of writing this guide, the following weather elements and their exact values can be observed in my city:
So, we've got the main weather elements figured out.
Read the second part of the guide where will deal with advanced weather parameters that are not in the usual weather forecasts: wind gusts, total accumulated precipitation, snow depth, atmospheric pressure at altitudes, optical phenomena — about two dozen in all. Most of them can only be found in professional weather apps and sites like the Windy.app for outdoor activities.
Text: Ivan Kuznetsov, an outdoor journalist, editor and writer from the Dolomites, Italy, and Karelia, Finland, with 10 years of professional experience. His favorite sports are hiking, cycling and sauna. Read his other articles
Cover photo: Garrett Parker / Unsplash