Hanoi’s average temperatures range from the low 70s in January to the 90s in July, though humidity is a constant. For the best overall experience, visit during autumn (September through November), when the weather is relatively mild, the humidity is lower, and the heavy rains of summer taper. It’s also when the Mid Autumn Festival (Tết Trung Thu), a lunar harvest festival typically held in late September or early October—and celebrated with traditional lion dances and moon cake pastries—takes place.
Spring (March and April) is also a worthwhile time to visit weather-wise, though for those looking to immerse themselves in a true Vietnamese experience, there’s no better time than Tết, the Vietnamese Lunar New Year, which usually falls in February. Along with traditional foods like banh chung (sticky rice cake), festivities include parades, colored lights and red banners, and an abundance of flower stalls. However, forget to plan ahead and Tết may be one of the worst times to visit, as many stores and restaurants are closed and travelers can end up paying a hefty price for lodging, transportation, and food.
Summer (May through August) is an option for those looking to explore Halong Bay or the city’s lakes, though if you’re not used to Southeast Asia’s heat, the days can be unbearably hot and humid—and the mosquitoes nasty. These months are also when the city sees the majority of its annual rainfall. While rain can occur year-round, the country’s “rainy season” typically begins in April and hits its peak in August.
Winter in Hanoi is relatively cool and dry, yet still humid.