The further you travel North or South of the Equator the colder average temperatures get. But different parts of the world with similar latitudes can have quite different climates. This page looks at factors that influence regional climate patterns.
factors that influence regional climate patterns
A range of hills can cause a rain shadow (low rainfall area) on the lee side to the prevailing weather fronts. This can cause a significantly lower than average annual rainfall than an area just a few kilometres away. The rain shadow effect is more pronounced with mountains but even low hills can cause the rainfall to be lower on the lee side.
Illustration showing how hills can create a rain shadow on the lee side of the prevailing weather fronts.
A valley can act as a cold sink. On still nights cold air sinks to the lowest point, which means in cool weather low lying areas usually have more frequent and severe frosts then the surrounding hills.
Water acts as a heat sink by absorbing heat when the weather is hot and slowly releasing it when the surrounding air temperature drops at night or when the weather cools down. This warming effect that water has means that land near a lake, river or the ocean tends to have fewer frosts and more mists and fog.
Fog is caused by warm air meeting surrounding colder air and condensing to form tiny water droplets. Fog may seem cold to humans but in fact, compared to surrounding temperatures, a fog is like a warm blanket. Even when fogs do not occur the presence of a large body of water will increase the air temperature of the surrounding land.
Temperature decreases with an increase in altitude because the atmosphere becomes less dense at higher elevations, resulting in fewer air molecules to absorb and retain heat, which leads to a decrease in the overall temperature. Temperature typically decreases by about 6.5 degrees Celsius per 1,000 metres of altitude gained.
Temperatures (especially night temperatures) will be colder at higher elevation and frost will be heavier and more frequent in the cooler months than at sea level.
Illustration showing how temperature drops as altitude increases.
Regional climate and your garden
The above factors mean that there can be considerable weather variations within a given region so it is important to take note of how these factors impact on your district and adjust your planting times and watering practices accordingly.
