Microclimates in Sydney

Several microclimates exist in Sydney, Australia, as described below.

Northern Coastal

This zone extends from Vaucluse in the south to Palm Beach in the north. Summer temperatures are tempered by blustery NE seabreezes and southerly changes, however nights are warmer here than anywhere else in the Sydney basin, with no frost days (minima less than 2 C). The western limit of this zone is a line from the Gadigal National Park to the CBD. The climate is comparable to San Diego, California (little diurnal variation).

The region is seldom affected by severe thunderstorms. Occasionally (mostly in Autumn and Spring) a cold pool of air travelling up the coast in the wake of a front will trigger coastal thunderstorms. An example of this phenomenon occurred in April 1999, the resulting hailstorm caused millions of dollars damage in coastal suburbs. Another notable event occurred in August 2006, when the inner Sydney region was blanketed with hail and graupel, giving rise to a "winter wonderland".

Indicative Suburbs: Manly, Mosman, Killarney Heights (on the border of the continental zone).

Indicative temperature range: 20-25 C (summer), 9-18 C (winter).

Southern Coastal

This zone extends from Bondi in the north to Bundeena in the south, its western boundary on a line from the CBD to Miranda (through the airport). Summer temperatures are similar to those in the northern coastal zone, however NE breezes are less intense, leading to warmer days on average. Southerly changes tend to impact this region more intensely than the north, and hence temperatures are 1 degree lower in this weather pattern. Overnight temperatures are lower as well, but frosts are a very rare event.

Like the northern coastal zone, the region is seldom affected by severe thunderstorms, but can be affected by post frontal cells.

Indicative suburbs: Coogee, Maroubra, Cronulla

Indicative temperature range: 18-26 C (summer), 8-17 C (winter).

Semi Continental

This area extends from the boundary of the coastal zones (see above) to the 151st Parallel east (a line from Dural to Holsworthy). Seabreezes will penetrate this area noticeably later than the coastal zones, and thus summer high temperatures are 1-3 degrees greater. Southerly changes penetrate this area well, hence the temperature differential is negligible in this particular weather pattern. Frost can occur but not very often, around once or twice per winter.

Severe thunderstorms tend to weaken over this region as they interact with seabreezes- the associated wind shear plays a critical role in decaying the core of these thunderstorms. As a result, the region receives less severe thunderstorms than western Sydney. The northern half of the region is prone to drifting thunderstorms from the Penrith area.

Indicative suburbs: Hornsby, Strathfield, Sutherland

Indicative temperature range: 16-28 C (summer), 6-16 C (winter).

Continental

All of the western suburbs are in this zone. Hot summer days with little or no seabreezes are the norm. Whilst summer maximum temperatures at the coast average 25 degrees C, the continental zone averages 30 C or more. Winter temperatures are lower than the coast; with frequent frosts. Richmond and Camden (both in this zone) have both recorded temperatures of -5 degrees C, whereas the corresponding extreme for Sydney Observatory Hill (in the coastal zone) is 2 degrees C.

The region often receives severe thunderstorms in summer that make their way over the Blue Mountains. In the summer of 2007-08, several hailstorms affected the western suburbs, one in particular causing widespread destruction in and around Blacktown.

Indicative suburbs: Penrith, Liverpool, Campbelltown

Indicative temperature range: 15- 31 C (summer), 3-16 C (winter).

Mountain

Confined to the Blue Mountains. The region is mild in summer, with average daytime temperatures of 22-24 C. Overnight temperatures are cool year round, however often not as frosty as the continental zone at sea level due to temperature inversions on the coldest nights. Winter temperatures are significantly colder than the Sydney basin, and snow can occur on higher ground west of Wentworth Falls (above about 800 m ASL). On average, there are 5 settling snowfalls per year in the upper Blue Mountains. Generally, a 1 degree drop in temperature is observed for every 200 m in elevation. Thus, daytime temperatures at Katoomba (1000 m ASL) are generally 5-6 degrees C cooler than Penrith at sea level, all other things held constant.

Severe thunderstorms often reach their maximum intensity in this region due to the confluence of dry air from west of the Great Dividing Range and humid air from the Pacific Ocean. As a result, hail to several cm in diameter is often reported in the upper Blue Mountains.

Fog is a common occurrence, particularly in winter. This keeps the diurnal range of temperatures comparatively low.

Indicative suburbs: Katoomba, Blackheath, Bilpin

Indicative temperature range: 12-23 C (summer), 3-10 C (winter)

Heat Islands

These areas tend to be hotter than the immediate surrounding area in most weather patterns. These are;

* Sydney Airport (due to reflected heat from the tarmac; creates urban heat island)
* Penrith Valley (hotter than other places in the continental zone due to topography)
* Sydney CBD (due to the urban heat island)

Cool Islands

These areas tend to be cooler than the immediate surrounding area in most weather patterns. These are;

* Canterbury (colder minimum temperatures in all seasons due to topography)
* Terrey Hills (due to elevation)
* Oatley (for unknown reasons, possibly topographic)