Mandaluyong City experiences the same climatic conditions prevailing over the whole of Metro Manila, which are being monitored by Station 430 of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) located at Science Garden in Quezon City.

There are two pronounced seasons:

• one dry from November to April,
• the other wet during the rest of the year.

PAGASA observations covering the period 1971-2000 reveal that the months of June to October normally had the most number of rainy days, with the month of August having the highest amount of rainfall at 526.8mm. Temperature is highest in April and lowest in January at 34.9°C and 20.4°C, respectively.

Generally speaking, the main Philippine air currents are divided into three groups:

1. the northern (loosely called Northeast Monsoon);
2. the equatorial air (loosely called the Southwest Monsoon); and
3. the trade winds, reaching the island from a generally easterly direction and coming from the tropical high pressure areas of the Pacific.

Because of topography and decided mountain ranges in the east, shielding Metro Manila and all the regions on the western part of the islands of Luzon, Mindoro, Negros and Palawan from the northern and in good part the trade winds, these regions are open only to the southwest monsoon and cyclonic storms.

A summary of climatological observations recorded by PAGASA from 1961 to year 2000 are shown in Table 1.02.