���˿���

Northern Ireland's location plays a very important part in the story of its weather and climate. Weather is the day to day condition of the atmosphere (the air all around a place). Climate is the average condition of the atmosphere measured over a long period (normally 35 years). Climate describes seasonal changes including normal temperatures and rainfall patterns for a place.

In Northern Ireland there are a number of different factors that are constantly at work to control the weather and climate through the year.

The closer a place is found on the earth to the Equator - the warmer this place will be. The North and South poles are extremely cold. The equator receives more solar energy because the sun passes higher in the sky. Due to the curve of the earth’s surface solar heat is more concentrated near the equator and less concentrated near the poles. Northern Ireland lies closer to the North Pole than to the equator.

The Prevailing wind is the wind direction that is the most common. Although the wind direction might sometimes come from the North East, South East or the North West – the prevailing wind in the British Isles comes from the South West. This means that Northern Ireland’s air most often comes from:

• further south so it is warmer
• from over the Atlantic Ocean so it is wetter

This helps to explain our mild and damp weather and climate.

Water takes a long time to heat up but also a long time to cool down. This means that water can hold its heat for much longer periods of time than the land.

• In summer coasts will be cooler as the sea warms slowly.
• In winter coasts remain warmer as water holds its heat for longer.

Northern Ireland is close to the sea and so it rarely gets either very hot or very cold (winter average is 4°C, summer average 17°C). Unlike Moscow, Russia is in central Europe far from the sea, which has a warmer summer and much colder winter (winter average is -8°C, summer average 20°C)

Places that are higher up hills and mountains will be colder than areas that are lower down. Within the atmosphere, for each 150m of altitude the temperature will fall by 1°C.

Northern Ireland experiences weather that changes frequently. Often, the weather that is experienced there at the start of the day will be very different from what is seen at the end of the day. Northern Ireland's weather can change quickly – which can make it difficult to forecast the weather for the week ahead.

One reason for these changes is the different air masses that effect our weather and climate. An air mass is a large body of air, even thousands of kilometres wide, with similar temperature and moisture content.

The air mass will start to form a long way from the British Isles and as it sits over an area – the air will start to pick up the temperature and moisture from that area. It will then start to move and be pushed towards the British Isles. You can tell a lot about what the weather will be like, just by knowing what direction the wind is coming from and which of the air masses is in control for that day.

There are four main air masses that bring different types of weather across the British Isles including Northern Ireland. Each of the air masses brings a set of different types of weather.

• Tropical – warmer air
• Polar – cooler air
• Maritime – damper air
• Continental – drier air