There are many short streams along this coast, fed by heavy rainfalls, but they have no geographic importance and no economic value under existing conditions.
As waterways all the rivers labour under the drawbacks of rapids, mud-banks at their mouths, banks overgrown with forest, sparse population, and currents liable to serious variations due to irregularity of supply from the mountains and sudden rainfalls.
A uniformly high temperature, excessive humidity, heavy rainfalls and violent tropical storms, known as typhoons or baguios, are characteristic of the Philippine climate.
The north-west counties are extremely wet; many localities here have normal rainfalls of 60-70 in.
Symons, F.R.S., of the Meteorological Office and of the Royal Meteorological Society, has resulted in the establishment of a vast number of raingauges in different parts of the United Kingdom, and it is generally, though not always, found that the mean rainfall over a long period can be determined, for an area upon which the actual fall is known only for a short period, by assigning to the missing years of the shortperiod gauges, rainfalls bearing the same proportion to those of corresponding years in the long-period gauges that the rainfalls of the known years in the short-period gauges bear to those of corresponding years in the long-period gauges.