Visitors head to Hanoi during all different times of the year but the busiest tourist season is during the summer months.  This is interesting because the summer is generally considered to have the worst weather in Hanoi.  Not only is it hot but but like many other places in SE Asia, it rains a lot during this time of year and can be quite humid.  Visitors who can avoid the major tourist months actually find that not only are the crowds thinner and the streets easier to negotiate but the weather is also nicer.

The average winter high temperature in Hanoi is approximately sixty five degrees and it rarely rains from November through February. This is why it is generally considered a favourable time for travelers to consider visiting the area.  There is also a large celebration in the area at the beginning of the year which many tourists enjoy.  Information on this celebration (called the Tet Nguyen Dan or simply the Tet) 

From February onward the rainy season begins, hitting its peak during April but continuing through the summer.  Summer high temperatures are generally in the nineties with thick humidity.

Updated weather information is available online from CNN.com or from Weather Underground. Up-to-the-minute weather at Hanoi's Noi Bai International Airport can be found here.