On April 5, 2025, the Huanan cloud system is making its eastward journey, bringing a noticeable increase in moisture across Taiwan. As a result, local short-term showers are expected in the northern, eastern, and central mountainous regions, as well as the Hengchun Peninsula. Meanwhile, sporadic short-term rain is also anticipated in the central plains. This weather shift comes as the country transitions from the pleasant conditions experienced during the Tomb Sweeping Day holiday.
The Central Meteorological Administration (CMA) has reported significant temperature drops in northern Taiwan, where daytime highs are now hovering around 20 to 21 degrees Celsius. In contrast, central and southern regions, including Taitung, are experiencing lows between 18 to 21 degrees Celsius. The CMA notes that the temperature difference between northern and southern Taiwan is quite pronounced, with the northern areas feeling noticeably cooler.
As the Huanan cloud system continues to influence the island, the rain is expected to taper off briefly tomorrow, April 6, but high moisture levels will persist. This ongoing weather pattern is likely to lead to further rain next week, particularly from April 7 to April 9, when the cloud system will weaken during the day but still bring occasional light rain, especially in mountainous areas.
Weather expert Wu De-Rong, in his column "Weather Secrets Classroom," explained that the latest European model simulations indicate that from the evening of April 9 to April 13, two shortwave troughs will pass through Taiwan successively. This will result in rapid changes between sunny and rainy conditions, with the potential for convective rainfall, thunderstorms, strong winds, and sudden heavy downpours. However, the timing of these weather events is still being refined, and residents are advised to stay tuned for updates.
Following the holiday, the CMA emphasizes that the rainy conditions will expand, particularly affecting areas north of central Taiwan. The forecast suggests that by April 10, regions north of central Taiwan will experience short-term showers or thunderstorms, with the possibility of localized heavy rain. Other areas will also see sporadic showers or thunderstorms.
In terms of air quality, the CMA has issued a general air quality alert for regions including Zhubei, Yilan, Hualien, Matsu, and Penghu. However, an orange alert has been raised for northern, central, and southern areas, indicating poorer air quality.
As the weather evolves, Wu cautions that although there is no significant cold air mass moving into Taiwan, the increased cloud cover and humidity will lead to cooler temperatures, especially in the north. Daytime highs in northern Taiwan are expected to range from 19 to 21 degrees Celsius, while central and eastern regions will see highs of 23 to 26 degrees Celsius. Southern Taiwan may still reach highs of 27 to 29 degrees Celsius.
Tonight into tomorrow morning, temperatures in open areas of central and northern Taiwan, as well as the northeast, could drop to between 14 and 16 degrees Celsius. In contrast, southern Taiwan and Hualien are expected to see lows of 16 to 18 degrees Celsius. The day-night temperature variations are particularly notable in central and southern regions.
As the Huanan cloud system moves eastward over the coming days, moisture levels over Taiwan are expected to decrease, leading to a shift in wind patterns to easterly and northeasterly. Rainfall will likely diminish, particularly in the western half of the island, which will transition to mostly cloudy or overcast conditions.
Looking ahead, the CMA forecasts that from April 7 to April 8, the lower atmosphere will maintain an easterly wind environment, while a shortwave trough will pass through the northern seas. Although there will be chances for the Huanan cloud and rain belt to continue moving eastward, the moisture is projected to be limited. Northern and eastern Taiwan will see thicker clouds and local short-term showers, while central and southern Taiwan will remain mostly cloudy with occasional sunshine.
By mid-April, another mid-level shortwave trough is expected to move eastward from southern China, potentially bringing low pressure and a frontal system over the northeastern seas. This could result in increased rainfall in central and northern Taiwan, with short-term showers and a possibility of thunderstorms. The southern region may also experience local short-term showers, albeit with less impact.
Despite these developments, Wu reassures that no significant cold air is predicted to follow the frontal passage, maintaining relatively mild temperatures across the island. Daytime highs in northern and northeastern Taiwan will range from 24 to 26 degrees Celsius, while central and eastern regions will see highs of 26 to 28 degrees Celsius. Southern Taiwan may still reach temperatures of 28 degrees Celsius or higher.
As the week progresses, the CMA advises residents to prepare for a variety of weather conditions, as the influence of the Huanan cloud system and frontal systems will bring about significant changes. The likelihood of rain will remain high, and the potential for thunderstorms could lead to more severe weather events. As always, staying updated with the latest forecasts will be crucial for planning outdoor activities.
