Vietnam has a tropical monsoon climate and a long-standing tradition of wet rice cultivation. The wet rice civilization has been formed and developed over more than four thousand years of building and defending the nation. Through generations of experience in farming, forestry, and seafaring, the Vietnamese people have created a rich treasury of weather-related proverbs, many of which remain relevant today.
In the field of fishing, especially among coastal fishing communities in Binh Thuan Province, a popular saying has been passed down through generations: “In the third lunar month, even old women go to sea.” This saying implies that going out to sea in the third lunar month is the best time—the peak of ideal conditions. The sea is unusually calm and crystal clear, so travelers do not have to fear seasickness. It’s also a wonderful time to enjoy the vast seascape. The water is so clear that from the deck of a boat, one can see coral reefs and marine life below.
Binh Thuan is one of Vietnam’s leading provinces for developing marine and island tourism, with destinations such as Cu Lao Cau (Tuy Phong District), Hon Ba (La Gi Town), and especially Phu Quy Island, which is frequently mentioned by both domestic and international tourists as one of the most beautiful resorts in the East Sea. As a result, the third lunar month attracts a large number of visitors to these islands for relaxation and sightseeing.
Therefore, the proverb “In the third lunar month, even old women go to sea” should be understood as referring to a time when the weather is favorable, and the sea is calm with gentle winds and light waves. To clarify this, I present some geographical knowledge for teachers to reference and for Binh Thuan residents to better understand the reasoning behind this traditional saying.
The strength of sea waves is closely related to wind levels. Since ocean waves are primarily caused by wind, stronger winds lead to bigger waves, and vice versa. (Waves can also be generated by other natural forces such as earthquakes, volcanic eruptions, or storms.) During the third lunar month, most days are characterized by light winds (levels 0–3), which are not dangerous, and wave heights average between 0 and 0.6 meters.
In Vietnam, two main types of winds are active:
The Northeast Trade Wind (Northern Hemisphere Trade Wind):
This wind originates from the subtropical high-pressure system over the Western Pacific Ocean (Tm) and blows into Vietnam from the northeast. It is typically dry and hot, with low humidity, and it occurs year-round. However, in Vietnam, this trade wind is often overshadowed by the monsoon winds and only becomes prominent when the monsoons weaken. During the winter, it contributes to dry and cold weather in various parts of the country. In the summer, it can cause heavy rains when active.
The Monsoon Winds:
These include the winter monsoon and summer monsoon, which alternate throughout the year. The winter monsoon (northeast monsoon) blows from November to April and creates different weather patterns across the country. Early winter in the north is often cold and dry, while late winter may bring drizzly, damp weather. The summer monsoon (southwest monsoon) blows from May to October, bringing hot, humid conditions and frequent thunderstorms and storms nationwide.
In addition to these major winds, there are also local winds such as the “bấc” (northerly), “lào” (hot dry wind from Laos), and “nồm” (southerly sea breeze).
The third lunar month, which corresponds roughly to April in the Gregorian calendar, is the transitional period when the northeast monsoon weakens and the southwest monsoon has yet to begin. During this time, the northeast trade wind from the southwestern edge of the subtropical high in the Western Pacific blows into Vietnam from the southeast. This wind causes humid, drizzly weather (known as “nồm”) in the Northern Delta, while in the South Central Coast, including Binh Thuan, the weather is sunny, dry, and experiences only gentle winds. The calm sea conditions are further enhanced by the meeting of trade winds from both hemispheres near the equator, which form upward convection currents, reducing surface-level wind activity.
During these days, the seas off Ninh Thuan and Binh Thuan typically experience light winds and calm waves, ideal for tourists—especially for marine and island tourism—as well as for fishermen going on offshore fishing trips. However, it is worth noting that climate change may cause occasional disruptions, and this folk proverb is primarily applicable to the coastal waters of the South Central region. In contrast, the Northern Delta and North Central provinces may still experience cold spells, as reflected in another saying:
“Cold stretches into the first month, sprouting cold in the second, and Bân’s cold in the third.”
This refers to lingering cold in the north, where late-season cold spells from the weakening northeast monsoon may still occur. The term “Bân’s cold” (rét nàng Bân) comes from a traditional folk tale and metaphorically refers to these final cold snaps of the season.
