On the north coast, and for some distance inland, the winds are north-west, monsoonal rains setting in at the end of October and lasting till the end of March or April, the heaviest rain being in December, January, and February, in which months the average at Port Darwin is 10.420, 14.782, and 13.009 inches, respectively.

The southerly reach of the north-west monsoon depends on the pressure in the interior, which is frequently very uniform. but when a barometric valley (vide maps 4 and 5) is formed the rains may extend almost without a break right across the continent, being in some years very heavy and general in South Australia. On the east coast summer rains are frequent and heavy, especially when tropical "lows" pass down from the north and north-east (vide maps 2 and 3).

In South Australia the prevailing wind in summer is south east, varied by hot, dry, northerly winds, as coastal "lows" approach from the west, followed on their retreating side by a sudden shift of wind to south-west and a rapid fall of temperature depression passes, the thermometer at times falling 30° or 40° in a few hours. I have known a fall of 20° in almost as many minutes.

From what I have said you will see that we have, as weather conditions:—

• 1st. A continual series of anticyclonic areas, which in the winter pass over the interior, covering the whole or greater part of the continent, with gradual falling gradients from the centre, while in the summer they pass along or near the south coast.
• 2nd. Cvclones, disturbers of the peace, but brining fruitful rains; sometimes, alas! disastrous floods. These are mostly of tropical origin, and, starting on a west to south-west course, they re-curve south of the trade belt, and move to the south-east. Some—those approaching from the north-east of Australia—strike the east coast of Queens land; others enter by the Gulf of Carpentaria, and, passing island, shed rains over the western interior of Queensland and New South Wales; others pass over the interior from the north-west; whilst others again pass to the west of Australia, and ultimately, rounding the Leeuwin, appear as a south coastal disturbance.
• 3rd. Northerly extensions of the antarctic low pressure, which, passing along the south coast, give us our winter rains, and, on their retreating side, south-westerly gales.

Bureau of Meteorology