Monsoon Systems

Taiwan’s climate is dominated by monsoon patterns: seasonal wind systems that reverse direction and bring markedly different weather conditions depending on the time of year. Understanding the monsoon is crucial to understanding Taiwan itself, as it fundamentally shapes not just the weather but the entire character of the island.

The Monsoon Phenomenon: Why Taiwan Is Uniquely Humid

The monsoon system represents one of Earth’s most important climatic phenomena, and Taiwan’s position makes it subject to the full force of the East Asian monsoon. To appreciate the monsoon’s significance, consider Taiwan’s latitude: between 22°N and 25°N. Look at other locations along this same latitude band around the world: the Sahara Desert in Africa, the Arabian Desert in the Middle East, the deserts of northern Mexico, and the arid regions of northern India before the Himalayas. These areas share Taiwan’s latitude but experience profoundly different climates: hot, dry, and often desert or semi-arid conditions.

Taiwan escapes this fate entirely because of the monsoon, which exists due to the fundamental thermal differences between large landmasses and oceans. During winter, the Asian continent cools rapidly whilst the Pacific Ocean retains heat, creating a pressure gradient that drives winds from land to sea. In summer, the pattern reverses: the continent heats dramatically whilst the ocean warms more slowly, drawing moist air from sea to land. This seasonal reversal, combined with Taiwan’s island position between the vast Asian continent and the even vaster Pacific Ocean, creates the moisture-rich environment that defines Taiwan.

The result is an island that receives abundant rainfall year-round, with most locations receiving 1,500mm–2,500mm annually, and some mountain areas exceeding 4,000mm. This moisture sustains Taiwan’s remarkable biodiversity, its lush mountain forests, its productive agriculture, and its distinctive landscape character. Without the monsoon, Taiwan at this latitude would likely resemble the arid landscapes found at similar latitudes elsewhere: dry hillsides, sparse vegetation, and water scarcity. Instead, the monsoon delivers such abundant moisture that Taiwan’s challenge is often managing excess water rather than scarcity¹.

This is not merely an academic point. The monsoon’s moisture explains why Taiwan looks and feels the way it does—why the mountains are perpetually green, why mould and humidity are constant domestic challenges, and why the air often feels thick and heavy. The monsoon is the fundamental reason Taiwan can support such dense vegetation and why, despite intensive development, the island remains remarkably green.

Northeast Monsoon

The northeast monsoon governs Taiwan’s weather from October through March, peaking in intensity from December through February. This system develops as cold, dry air from the Siberian high-pressure system moves southward across the Asian continent, gaining moisture as it crosses the East China Sea before striking Taiwan’s northeast-facing coasts and mountains.

The geographic impact is dramatic and visible. The northeast coast, particularly areas around Keelung and the northeast corner near Yilan, receives rainfall during this period, whilst areas in the rain shadow of the mountains remain relatively dry. Hsinchu, positioned where the Central Mountain Range bends inland, experiences powerful winds funnelled through the geographic gap, earning its reputation as the “windy city”. These sustained winds, combined with clear skies in the northwest, create ideal conditions for the region’s wind power generation.

The monsoon’s effects extend beyond precipitation. It brings cooler temperatures, with occasional cold surges dropping temperatures across the island, sometimes even bringing rare snow to high mountains or, extraordinarily, to elevations as low as 1,000 metres during intense events. The persistent cloud cover in northern Taiwan during this season affects mood and behaviour: you’ll notice locals treasure any appearance of blue sky during these months.

For travellers, understanding the northeast monsoon explains why winter itineraries shouldn’t simply replicate summer plans. The north’s best outdoor venues, like beaches, coastal hikes, mountain trails, often experience poor conditions from December through March, whilst the same period offers excellent weather in the south. The monsoon effectively divides the island into two different climate experiences for half the year.

Southwest Monsoon

The southwest monsoon operates from May through September, though its effects are generally less dramatic than its northeast counterpart. Warm, moisture-laden air flows from the South China Sea and Indian Ocean, bringing humidity and contributing to summer rainfall, particularly in southern and western Taiwan.

Unlike the northeast monsoon’s persistent rain, the southwest monsoon primarily enhances convective activity: it doesn’t necessarily bring continuous rainfall but increases the intensity and frequency of afternoon thunderstorms. The moisture it carries, combined with strong solar heating, creates the characteristic summer weather pattern: clear mornings giving way to towering cumulus clouds by early afternoon, then explosive thunderstorms that release enormous amounts of rain in short periods before clearing by evening.

The southwest monsoon also interacts with typhoons and tropical disturbances. When a typhoon’s outer circulation combines with southwest monsoon flow, the result can be exceptional rainfall, particularly in southern and central Taiwan. Some of Taiwan’s most severe flooding events have resulted from this interaction rather than from typhoons alone.