The area of Australia subject to a rainfall of from 10 to 20 in. is 843,000 sq. m. On the seaward side of this area in the north and east is the 20 to 30 in. annual rainfall area, and still nearer the sea are the exceptionally well-watered districts. The following table shows the area of the rainfall zones in square miles:—
| Rainfall. | Rainfall Area in sq. m. |
| Under 10 inches | 1,219,600 |
| 10 to 20 ” | 843,100 |
| 20 to 30 ” | 399,900 |
| 30 to 40 ” | 225,700 |
| 40 to 50 ” | 140,300 |
| 50 to 60 ” | 47,900 |
| 60 to 70 ” | 56,100 |
| Over 70 ” | 14,100 |
| ———— | |
| Total | 2,946,700 |
The tropic of Capricorn divides Australia into two parts. Of these the northern or intertropical portion contains 1,145,000 sq. m., comprising half of Queensland, the Northern Territory, and the north-western divisions of Western Australia. The whole of New South Wales, Victoria and South Australia proper, half of Queensland, and more than half of Western Australia, comprising 1,801,700 sq. m., are without the tropics. In a region so extensive very great varieties of climate are naturally to be expected, but it may be stated as a general law that the climate of Australia is milder than that of corresponding lands in the northern hemisphere. During July, which is the coldest month in southern latitudes, one-half of Australia has a mean temperature ranging from 45° to 61°, and the other half from 62° to 80°. The following are the areas subject to the various average temperatures during the month referred to:—
| Temperature Fahr. | Area in sq. m. |
| 45°-50° | 18,800 |
| 50°-55° | 506,300 |
| 55°-60° | 681,800 |
| 60°-65° | 834,400 |
| 65°-70° | 515,000 |
| 70°-75° | 275,900 |
| 75°-80° | 24,500 |
The temperature in December ranges from 60° to above 95° Fahr., half of Australia having a mean temperature below 84°. Dividing the land into zones of average summer temperature, the following are the areas which would fall to each:—
| Temperature Fahr. | Area in sq. m. |
| 60°-65° | 67,800 |
| 65°-70° | 63,700 |
| 70°-75° | 352,300 |
| 75°-80° | 439,200 |
| 80°-85° | 733,600 |
| 85°-90° | 570,600 |
| 90°-95° | 584,100 |
| 95° and over | 135,400 |
Judging from the figures just given, it must be conceded that a considerable area of the continent is not adapted for colonization by European races. The region with a mean summer temperature in excess of 95° Fahr. is the interior of the Northern Territory north of the 20th parallel; and the whole of the country, excepting the seaboard, lying between the meridians of 120° and 140°, and north of the 25th parallel, has a mean temperature in excess of 90° Fahr.
The area of Australia is so large that the characteristics of its climate will not be understood without reference to the individual states. About one-half of the colony of Queensland lies in the tropics, the remaining area lying between the Queensland. tropic and 29° S. The temperature, however, has a daily range less than that of other countries under the same isothermal lines. This circumstance is due to the sea-breezes, which blow with great regularity, and temper what would otherwise be an excessive heat. The hot winds which prevail during the summer in some of the other colonies are unknown in Queensland. Of course, in a territory of such large extent there are many varieties of climate, and the heat is greater along the coast than on the elevated lands of the interior. In the northern parts of the colony the high temperature is very trying to persons of European descent. The mean temperature at Brisbane, during December, January and February, is about 76°, while during the months of June, July and August it averages about 60°. Brisbane, however, is situated near the extreme southern end of the colony, and its average temperature is considerably less than that of many of the towns farther north. Thus the winter in Rockhampton averages nearly 65°, while the summer heat rises almost to 85°; and at Townsville and Normanton the average temperature is still higher. The average rainfall along the coast is high, especially in the north, where it ranges from 60 to 70 in. per annum, and along a strip of country south from Cape Melville to Rockingham Bay the average rainfall exceeds 70 in. At Brisbane the rainfall is about 50 in., taking an average of forty years. A large area of the interior is watered to the extent of 20 to 30 in. per annum, but in the west and south, more remote than from 250 to 300 m., there is a rainfall of less than 20 in.
Climatically, New South Wales is divided into three marked divisions. The coastal region has an average summer temperature ranging from 78° in the north to 67° in the south, with a winter temperature of from 59° to 52°. Taking the New South Wales. district generally, the difference between the mean summer and mean winter temperatures may be set down as averaging not more than 20°, a range smaller than is found in most other parts of the world. Sydney, situated in latitude 33° 51′ S., has a mean temperature of 62.9° Fahr., which corresponds with that of Barcelona in Spain and of Toulon in France, the former of these being in latitude 41° 22′ N. and the latter in 43° 7′ N. At Sydney the mean summer temperature is 70.8° Fahr., and that of winter 53.9°. The range is thus 16.9° Fahr. At Naples, where the mean temperature for the year is about the same as at Sydney, the summer temperature reaches a mean of 74.4°, and the mean of winter is 47.6°, with a range 26.8°. The mean temperature of Sydney for a long series of years was spring 62°, summer 71°, autumn 64°, winter 54°.
Passing from the coast to the tableland, a distinct climatic region is entered. Cooma, with a mean summer temperature of 65.4°, and a mean winter temperature of 41.4°, may be taken as illustrative of the climate of the southern tableland, and Armidale of the northern. The yearly average temperature of the latter is scarcely 65.5°, while the summer only reaches 67.7°, and the winter falls to 44.4°.