Page:The climate of Western Australia, from meteorological observations made during the years 1876-1899.djvu/38

 and the total amount registered on Saturday at 9 a.m. for the preceding 24 hours was 265 points. This constitutes a record as far as the Observatory is concerned, and the amount recorded at the Botanical Gardens, viz., 271 points, has only twice been exceeded since the records commenced in 1876. The two exceptions were in July, 1891, when 3 inches fell, and in May, 1879, when 280 points were registered. The actual number of rainy hours during one day has been exceeded only once since pluviometer records commenced in April, 1897. Between last Friday and Saturday mornings at 9 o'clock it was actually raining for 10 hours 12 minutes, and during the day ending 9 a.m., September 30th, 1897, there were 12 hours 48 minutes of actual rainfall, but the total quantity then was only 60 points, and most of this fell during the night. This morning (Sunday) 72 points, and this evening at 6 p.m. 80 points, were registered, making a total of 4 inches and 17 points between Friday morning and Sunday evening. The amount so far recorded for this month is 731 points, or nearly an inch in excess of the average for the whole month for previous years. The greatest quantity ever registered in Perth for the month of June was 12⋅11 inches in 1890.

Owing to this tendency for the rain to fall principally in heavy showers and at night, and to the sandy nature of the soil, which rapidly absorbs it, the general impression of the Perth winter is that of a succession of fine, bright, calm days, varied occasionally by a severe but brief storm. The weather is on the whole delightful, but it may perhaps be too mild. One misses the keen frosty feeling that is experienced in other places, and its absence probably justifies to some extent the popular statement that the climate is enervating.

At night it is frequently cold however, July showing an average of 8 nights during which the minimum thermometer in the screen registers below 40 degrees. (As this description of Perth is to be, taken as representing more or less the whole of the South-West district it must be stated that severe frosts are by no means uncommon inland. The coldest part of the Colony at night is between Southern Cross and Katanning, and here the thermometer frequently falls below 32 degrees, especially if exposed to radiation. The mean minimum in the Stevenson screen for July is 39⋅1 at Southern Cross and 39⋅5 at Katanning.)

Very severe floods have been occasionally experienced at Perth and elsewhere in past years, but not since systematic records commenced.

The summer does not set in quite so abruptly as the winter. With an occasional hot day in October it commences generally in November, but does not as a rule become really noticeable until after Christmas. Taking a temperature of 90 degrees in the shade as the criterion of a hot day, we find an average of less than 1 in October, 4 in November, 7 in December, 12 in January, 12 in February, 9 in March, and 2 in April. This number (47 in all) seems rather formidable, but the heat is not, as a rule, felt oppressively on account of the short portion of the day during which it lasts on each occasion. On a normal hot summer day a sea breeze always sets in about noon on the coast, and reaches Perth about 2 p.m. The temperature then commences to fall, and the evening and night are delightfully cool and pleasant. Occasionally a protracted spell of hot weather is experienced, but even then the nights are generally cool. An interesting table is given on page 26. This includes all the "heat waves," as they are popularly termed, which have passed over Perth since January 1st, 1880, and it will be noticed that hot nights are distinctly exceptional, even during these specially selected hot periods. The longest of these spells without a break occurred in 1896, when the maximum exceeded 90 degrees on every date between January 25th and February 12th, nineteen in all; but the most severe heat was apparently in January and February, 1880. The highest reading that has so far been recorded in Perth is 116⋅7, which occurred in January, 1878.

Notwithstanding the fact that the monthly means are as a rule higher than those for the principal cities in South Australia, Victoria, and New South Wales, and that we are in a lower latitude than any of these, the same remark may be applied to the summer climate as to the winter. It appears to be milder than the others. One notices the absence here of those violent changes which are sometimes experienced in the other colonies. When a cool change comes after a spell of hot weather it seems to steal upon the land gradually. The appearance of soft watery cumulus clouds in the West, generally about sunset, announces the arrival of the welcome change. That evening will be cooler than the preceding ones, but not remarkably so, and next day it may be more or less cloudy, but only moderately cool. At night probably a few light showers, and we realise that a definite change has occurred. Whether or not the sudden changes experienced elsewhere act as a tonic it is difficult to say, but, at all events, they rarely if ever occur in Perth.

A curious instance of uniformity is afforded by the figures showing the average summer temperatures since 1876. One frequently hears the expression "A remarkably cool summer," or "A terribly hot summer," "A real scorcher," etc., yet we find that although the means for the individual months may vary considerably, those for the summer (November to March) diverge but little from the general average. It must be remembered, in studying the following figures, that the thermometers were transferred from one locality to another in August, 1885, and, therefore, the two periods 1876-1885 and 1886-1899 must be studied separately. So uniform on the whole are the figures, and so distinct the break, amounting to 2∘⋅1, that the change in the method of exposure was ascertained by means of it.