Lowland areas of North Luzon adhere to the standard Philippine monsoon climate, with a long dry season from November to May and a shorter wet season from June to October. December and January are the most pleasant months, with centigrade temperatures dropping into the low 20s and getting cooler and drier the further north you go. The April-to-June period is brutally hot throughout the lowlands. Typhoons start storming up the Pacific in July but usually only make direct hits on the northeast and Batanes. Beware: you could get stranded for days in Batanes when a typhoon gallops through. The rains are most intense in August and September.
The highlands are a different story. The Cordillera is liable to get rain any time of the year, but the rains are particularly intense from May to September and the higher the elevation, the more intense the rains. Landslides often disrupt travel on the spectacular dirt 'highways' of the Cordillera during this time. Between November and February it can get quite cool in the highlands; around Christmas, night-time temperatures can drop into the single digits at elevations over 1000m.