32. The provinces of Cagayan and Aurora often experience heavy rains and flooding compared to Ilocos regions because of the Sierra Madre Mountain Range.

The Sierra Madre Mountain Range, the longest mountain range in the Philippines, acts as a natural barrier to the provinces of Cagayan and Aurora. When moist air from the Pacific Ocean hits the eastern side of the Sierra Madre, it rises and cools, leading to condensation and precipitation. This is known as orographic rainfall.

As a result, the eastern side of the Sierra Madre, where Cagayan and Aurora are located, receives a high amount of rainfall. On the other hand, the Ilocos region, located on the western side of the Sierra Madre, is in the rain shadow of the mountain range. This means it receives significantly less rainfall because the air that reaches it has lost most of its moisture on the eastern side of the mountains.

Therefore, the Sierra Madre Mountain Range is the reason why Cagayan and Aurora often experience heavy rains and flooding compared to the Ilocos region.