regional climateThe planet's climate is not stable. If it was then the further you travelled North or South of the Equator the steadily colder it would get. But in fact different parts of the world with similar latitudes can have quite different climates.
For example London, with a latitude 51º North, has a much milder Winter climate than New York with a latitude of Just 40º North (closer to the equator than London). This is because a warm current, (known as the North Atlantic current or drift) runs up the East coast of the Atlantic and, by giving off heat into the atmosphere, creates a warmer climate in that region. The West coast of the Atlantic (America's Eastern Sea board) has no such warm current to act as a buffer in Winter and therefore is much colder. London has an average maximum temperature in January of 8 degrees Celsius while New York's is 0 degrees.
The North Atlantic current has an extremely powerful and wide spread effect on much of coastal Europe. But there are other much more numerous examples of the physical landscape effecting the climate of regional and sub regional areas. For example :-
Hills can create a rain shadow on the lee side of prevailing weather fronts.
A range of hills can cause a rain shadow (low rainfall area) on the lee side to the prevailing weather fronts.
A valley can act as a cold sink. On still nights cold air always 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 large body of water will increase the surrounding air temperature.
These are just a few of examples there are of how physical conditions can impact on regional climates. Understanding the influences on the climate in your region will better help you understand gardening conditions in your own back yard.