Weather in the Philippines generally falls into two categories: dry and wet season, although one source suggests that there are four different climatic regions in Philippines:

 http://en.wikipedia.org/wiki/Climate_...

 Note that it may be advantageous to visit Mindanao or parts of the Visayas when the weather on Luzon might not be at its best. 

The dry or summer season begins mid-March and ends during the last week of June.  Although these months are considered as the peak of heat in the country, it can start as early as late February and may linger until early July.  Wet season is also known as typhoon season.  Strong winds, heavy downpour and flooding is commonly experienced during the months of July to September, most noticeably in Metro Manila and the northern part of the most populous and largest island, Luzon. 

 While October to January may or may not experience typhoons, these months bring in cool and calm weather throughout the country.  It is said that the best time to go to Philippines is during the Christmas to post-holiday (January to late February) season when the weather is calmer and the heat is not as scorching as during the months of March, April and May.  But one should plan ahead if travelling during this season since accommodations and flights tend to be fully booked as many Filipinos working abroad go back home for the holidays.

It is advised to wear comfortable and loose clothing, as it is generally accepted in public.  Sandals, rubber shoes, hats, shorts or skirts are a staple when going to the islands.  But it is advisable to wear appropriate and decent clothing if one will visit offices, churches and fine-dining areas.  For males, wear long pants.  

Here are links to weather forecasts for Manila and a variety of locations around the 7107 islands of Philippines. Click on the city or location name for more detailed local information.

http://www.pagasa.dost.gov.ph/wb/wxfc...

Manila - 5 Day Weather Forecast Info

Philippines Weather Forecast info - (Select a Location)