By Ellalyn de Vera Ruiz Daylight and darkness will be almost of equal length this Friday, March 20, which is one of only two occasions in every year. According to the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA), vernal equinox is an astronomical event that marks the beginning of spring in the northern hemisphere and autumn in the southern hemisphere. The Philippines is above the equator and part of the northern hemisphere. Although there is no spring season in the country, warm and dry season prevails from March until May. On the day of the vernal equinox, PAGASA said night and day are about the same length in both hemispheres. Days will begin to last a little longer and nights get a bit shorter in the country after the vernal equinox. Every year, equal lengths of day and night happen twice a year during the vernal and autumnal equinox, on March and September, respectively. 'Amihan' fizzles PAGASA has yet to officially declare the end of the northeast monsoon or "amihan" season this year. The prevalence of easterlies, a weather system associated with the warm weather, is one of the manifestations of the impending end of the cold and dry "amihan" season. Last year, PAGASA declared the end of "amihan" and start of warm and dry season on March 22. This weekend, PAGASA said the easterlies or the warm and humid winds coming from the Pacific will be the dominant weather system that will bring partly cloudy to cloudy skies with isolated rain showers over the entire archipelago. The hot and humid mornings could trigger possible flash floods or landslides during severe thunderstorms mostly occurring in the afternoon or evening. PAGASA earlier said it may declare the termination of "amihan" season, and the official onset of warm and dry season in the country, towards the end of the month.