micro climate
By micro climate I mean the unique mini climate of each garden block. The micro climate of a garden can vary significantly even from gardens just a few metres away.  They even create temperature variations within your own backyard.  This is due to a number of factors.

the slope of the garden
Illustration of backyard heat sinks and frost points
On cold nights brick walls, concrete paths and ponds will act as heat sinks while frost will settle on lower slopes.
Frost will tend to settle at the bottom of a slope.

the direction your block faces
North (South in the Northern hemisphere) and West facing blocks can be much hotter, South facing blocks will generally be cooler as they are likely to be shaded more.

the presence or absence of large trees
Shady trees will make your garden much cooler in Summer than a treeless block.  In the cooler months trees, will also offer a measure of protection against  frosts, especially if they are evergreens.

the presence of concrete paths, brick walls and ponds
These will act as heat sinks, absorbing the sun's heat during the day and slowly releasing it at night. They can offer good protection against frost on cool nights.  Ponds will also have a cooling effect in hot weather.

It is possible to change the microclimate of your garden by adding or removing some of the above mentioned items.   For some hints on how to do this see MICRO CLIMATE CONTROL on  the old Urban Food Garden website.