The lowest temperature recorded during ten years by Staff-Surg. J. Campbell, R.N., from whose observations these notes are compiled, was 57° F. (13·9° C), and the highest 97·5° F. (36·4° C). December is the driest, and September the moistest month of the year, and hail fell once in fifteen years. Droughts are rare. The south-west monsoon becomes weak in September. Early in October northerly breezes set in, varying at first to east and west of north, and by November the north-east monsoon is established, to reach its strongest in December, and then gradually failing till early in March, when the “Kiti” breezes—south to south-south-west—usher in the monsoon. From May to August the winds are sometimes boisterous. The above remarks apply to Lower Siam and to Bangkok in particular, for which the table below, compiled from Campbell’s figures, gives the main climatic data.
| Bangkok. Lat. 13° 58′ N.; Long. 100° 34′ W.Near Sea-level. | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Month | Mean Temperature | Mean Maximum Temperature | Mean Minimum Temperature | Relative Humidity | Rainfall | Number of Rainy days | ||||
| F. | C. | F. | C. | F. | C. | Ins. | Mm. | |||
| January | 76·1 | 24·5 | 87·7 | 30·9 | 69·4 | 20·7 | 75 | 0·09 | 2·4 | 2 |
| February | 79·1 | 26·2 | 88·6 | 31·5 | 74·1 | 23·4 | 78 | 0·56 | 14·2 | 7 |
| March | 82·5 | 28·1 | 93·0 | 33·9 | 74·5 | 23·6 | 74 | 0·83 | 21·4 | 1 |
| April | 83·4 | 28·5 | 94·1 | 34·5 | 79·0 | 26·1 | 75 | 2·42 | 51·1 | 10 |
| May | 82·3 | 27·9 | 89·7 | 32·0 | 76·8 | 24·8 | 78 | 10·54 | 268·0 | 20 |
| June | 82·3 | 27·9 | 89·4 | 31·8 | 78·1 | 25·7 | 78 | 7·72 | 195·7 | 16 |
| July | 81·4 | 27·4 | 88·1 | 31·2 | 76·2 | 24·5 | 78 | 8·02 | 204·0 | 26 |
| August | 81·4 | 27·4 | 89·0 | 31·7 | 76·2 | 24·5 | 79 | 5·65 | 143·5 | 17 |
| September | 80·3 | 26·8 | 88·6 | 31·5 | 76·7 | 24·8 | 82 | 11·30 | 287·0 | 22 |
| October | 80·1 | 26·7 | 87·3 | 30·7 | 75·1 | 24·0 | 82 | 7·46 | 189·3 | 14 |
| November | 76·8 | 24·9 | 83·7 | 28·8 | 70·3 | 21·3 | 77 | 2·36 | 59·8 | 6 |
| December | 74·8 | 23·8 | 81·6 | 27·6 | 63·3 | 17·4 | 74 | 0·09 | 2·4 | 2 |
| Year | 80·1 | 26·6 | 88·4 | 31·3 | 74·1 | 23·4 | 77 | 67·04 | 1703 | 143 |
Some authorities make the rainfall of Bangkok considerably less, but Campbell’s observations extended over several years and may perhaps be preferred. The delta of the Menam River is annually flooded between June and November, and the spring levels are close to the surface all the year round. North of the delta of the Menam is the Korat Plateau, some 700 feet above the sea-level, a wilderness of shadeless bush, interspersed with salt marshes. One of the main drawbacks of the country is the scarcity of potable water, the supplies both in the Menam delta and on the Korat being almost always brackish and a nearly certain cause of digestive disturbance for Europeans, who thus have to rely greatly on aerated waters imported from the Straits.
Upper Siam, on the other hand, enjoys a dry climate with cool nights, but speaking generally the climate is an exceptionally trying one for European residents.
Cochin China
has a moist, hot climate. During the dry season, which lasts from November to April, the temperature varies from 95° F. during the day to 63° F. at night (35° to 17° C.), whereas during the rains, which last from May to October, the range of variation is only between 86° and 68° F. (30° to 20° C.); the relative humidity at this season reaching 89 per cent. Further north, in Tongking, the range of temperature is wider, from 99° to 18° F. (36° to -7° C.). The rainfall is much heavier than in Siam; Saigon, lat. 10° 47′ N., receiving its maximum of 17·7 ins. (423 mm.) in September and a total rainfall of 74 ins. (1,873 mm.); while at Hue, lat. 16° 33′ N., the wettest month is October, with 26·15 ins. (664 mm.), and a total of 102 ins. (2,592 mm.). Further north, at Hai-fong, in lat. 20° 57′ N., the most rainy month is August, with 14·8 ins. (374 mm.). July falls but little short of this, but the total is less than that of the other two stations, amounting to no more than 64 ins. (1,627 mm.).
The change to the north-east monsoon in November is not unfrequently marked by sudden and devastating storms. The climate has a very bad reputation, malaria, dysentery of a peculiarly deadly type, and diseases due to internal worms, being very common, especially during the rainy season.
China.
—Owing to the backward state of the country, there is singularly little information of a definite character available with respect to the enormous Chinese Empire, the entire southern half of which comes within the scope of the tropical climatologist. In the south, regular observations are carried on in the British colony of Hong Kong, and in the north at Zi-ka-Wei, near Shanghai, an admirably conducted observatory is conducted by the Jesuit missionaries, who so often enrol themselves as the pioneers of science.
Speaking generally, however, whether in the case of littoral or continental climates, those of China appear to compare favourably with localities of the same latitude in India and the Indo-Malay peninsula.