1. The onset of rainy season heavily relies on Climate Type I areas.
The rainy season or wet season is a time when the country receives rains from various weather systems such as southwest monsoon or habagat, intertropical convergence zone (ITCZ), low pressure area (LPA), and tropical cyclone (TC). However, we only need to observe the rainfall and prevailing winds among Climate Type I areas before declaring the rainy season. These are located somewhere in the western part of Luzon and Visayas (blue areas).
2. There are more tropical cyclones on a rainy season than the rest of the year.
The rainy season in the country usually begins in June and lasts for 5 months. An average of 12 TCs enters the Philippine Area of Responsibility (PAR) during this time, which accounts for 60% of the total average TCs entering a year. While some people associate the rainy season with the typhoon season, note that they are not the same and that the peak of the typhoon season only happens during the wet season.
3. It is NOT always raining during the rainy season.
Yes, you heard it right: it’s not always raining in the rainy season as it’s not always dry in the dry season. Sometime during the wet season, you may come across the term monsoon break. This pertains to a period when the country experiences mostly fair, if not fine, weather conditions due to the absence of habagat. Monsoon breaks last between a few days to two weeks.
4. The term habagat season is more colloquial than formal.
If the term habagat season refers to a time when the southwest monsoon is prevailing, then it starts a few days before the rainy season onset and ends a few days before the latter terminates. Thus, the rainy season and habagat season cannot be used interchangeably. Rains during the wet season are not solely caused by the southwest monsoon, anyway.
5. An enhanced habagat means serious trouble.
Enhanced habagat pertains to strong winds directed towards a weather disturbance. These winds from the west are warm and humid. When an LPA or a tropical cyclone is located east of the country, the enhanced southwest monsoon will likely cause downpour and swells on the western side of the country and may last for several days. Examples of this are the habagat enhanced by Typhoon Ondoy (Ketsana) in September 2009 and Typhoon Haikui in August 2012.