Atmosphere And Weather

Weather Symbols

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Have you ever wondered what the blue Hs stand for on a traditional weather map? How about those long blue lines that have triangles? Weather maps have many symbols on them, and while it’s understandable that some people get confused about them, they’re not that difficult to learn after all.

To familiarize yourself with weather symbols, it’s best to know the general basics of the weather conditions. Precipitation is something people look for before they head outside or have plans. They want to know if it’s going to rain or snow, or if the weather will stay dry and sunny. Depending on the time of year, you yourself may think about what you need to wear. If the weather’s cool, it may be necessary to wear a jacket or sweater. If the temperatures are hot, you won’t need to wear as much clothing.

High and low pressure systems

The blue Hs that you see on any weather map stand for high pressure. A high pressure system generally means calm, perhaps sunny weather. There’s virtually no precipitation nearby, so no inclement weather is expected.

The red Ls mean low pressure. It’s basically the opposite of high pressure; a low pressure means unsettled weather. Many types of storms are associated with low pressure systems. They include severe thunderstorms, blizzards, and tropical depressions.


The blue lines with pointy triangles are a cold front. Cold fronts usher in cooler, drier air behind them. But what’s ahead of them may be a surge of warm air, along with some showers or thunderstorms.  

Red lines with semi-shaped circles are known as a warm front. They are also responsible for bringing stormy weather. When a warm front moves northward, so does warmer air mass.

A stationary front is a front in the form of both triangles and red semi-circles. They usually don’t move very much. Once they slowly move, a “train” of showers/thunderstorm clusters form along them. Cooler air stays above a stationary front and warm air is bottled up beneath it.


When you see those bright white lines that are drawn around a high or low pressure, you’re seeing isobars. Isobars help measure the atmospheric pressure around weather systems. They also circle around the cores of high and low pressure systems.


The most common type of precipitation is rain. When rain shows up on a radar map, it’s usually in green that moves when the radar is in motion. The heavier the rain, the darker the colors get. Light rain is light green, but very severe thunderstorms with heavy rain can be shown in dark red or bright pink. Snow is usually in blue colors, and again, the heavier the snow, the darker color it appears on the weather map. Other types of frozen precipitation are freezing rain and sleet, and their colors usually show up in pink.

These are the most common symbols you often see on a map. Understanding them can indeed help you get ready for the weather ahead. That’s the role of meteorologists, too. They predict weather to help you stay prepared.

More about this author: Sam Smart

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