Best Time to Cruise the Mekong River

The best time to cruise the Mekong River depends on one choice: cool, dry weather from November to February, or high water that opens the Tonle Sap lake to vessels from mid-August to November. High water lasts about 3.5 to 4 months, and one month, November, sits in both windows. Plan for the days up to mid-November, because some operators end high water near that date and the dates vary each year. This page gives weather, rain, lake level, and crowds for each month, shows how your route changes the answer, and ends with the months to avoid. Choose the month by what you need from the river, then check how your operator handles low water.

Calypso Mekong runs one vessel on the Saigon to Siem Reap route; it appears once, in the section on how a six-guest vessel handles the water season.

When Is the Best Time to Cruise the Mekong River?

The Mekong runs on two calendars. The weather calendar is cool and dry from November to February, and the water calendar is high from mid-August to November. November sits in both, and in high water a vessel can cross the Tonle Sap lake.

High water is the period in which the lake is deep enough for a river vessel to enter, and low water is the period in which it is not. The Mekong River Commission (MRC) reports reverse flow status in its
wet-season bulletins and records the start of reverse flow into the lake between late May and mid-June.
Operators open the lake to vessels from about mid-August, once depth passes their minimum.

The table sets the two calendars side by side.

The rows run from the weather window to the water window to their overlap.

Pick the weather window for comfort, the water window for the lake, and 1–15 November for both. From December
to April, rain stays at 2.5 in (63 mm) or less a month in both Ho Chi Minh City and Phnom Penh (climate normals,
read 6 October 2026).

One claim holds that the dry season suits every Mekong cruise. The dry season suits the weather. Access to the lake
depends on water, and some operators run a road transfer when the lake is low.

What Do Weather, Rain, Lake Level and Crowds Look Like Month by Month?

Heat changes little through the year, while rain, lake level, and fares change a lot. Daily highs in Ho Chi Minh
City stay between 89°F and 95°F (31.6–34.9°C), and rain peaks in September at 10.7 in (273 mm) in
Ho Chi Minh City and 10.0 in (253 mm) in Phnom Penh. "Cool" means nights of 71–75°F
(21–24°C), not a cool day.

Normals are long-term averages, so a single year can differ. Peak season is the set of months in which operators
charge their highest fares. The table gives one row for each month.

The rows run from January to December, and the lake column follows the MRC calendar.

Sources: WMO climatological normals from the Viet Nam Meteorological and Hydrological Administration (Ho Chi Minh
City, 1991–2020) and Cambodia's Ministry of Water Resources and Meteorology (Phnom Penh, 1982–2024),
as supplied ; lake records from the MRC
data portal (read 6 October 2026); peak-season months from operator season calendars . Phnom Penh highs
sit within 4°F (2°C) of the Ho Chi Minh City highs in every month.

What Does Each Season Look Like on the Water?

A traveller meets three seasons on the river: cool and dry from November to February, hot and dry from March to
May, and green with high water from June to October, when the lake opens to vessels from mid-August.

Cool and dry (November to February): nights fall to 74–75°F (23–24°C) in Ho Chi Minh City from
December to February and to 71°F (21–22°C) in Phnom Penh in December and January. Skies stay clear,
and rain stays at 2.5 in (63 mm) or less a month from December to April, so the sundeck stays dry.

Hot and dry (March to May): daily highs reach 92–95°F (33.6–34.9°C) in Ho Chi Minh City, and
the lake sits at its low point in April and May.

Green (June to October): rain falls on 13 to 19 days a month in Ho Chi Minh City from May to October, counting days
of 0.1 mm or more. Showers usually come in the afternoon and last about an hour . Rice fields and banks turn green.

How Does the Tonle Sap Lake Rise and Fall Through the Year?

The Tonle Sap lake fills and empties once a year. From late May to mid-June, the Mekong rises above the lake and
pushes water up the 75 mi (120 km) Tonle Sap River into it. The lake grows five to six times in area and reaches
20–30 ft (6–9 m) deep at its peak.

The Tonle Sap River runs between the lake and the Mekong at Phnom Penh, and the direction of its flow follows the
difference in water level between the two. The table traces the lake through one year.

The rows follow the lake from its dry-season trough through one full cycle.

The MRC records these levels at two stations: Kampong Luong, inside the lake, and Prek
Kdam, on the Tonle Sap River, which publishes daily water levels (MRC, read 6 October 2026). The MRC
data portal holds the validated daily readings, and the wet-season
bulletins track reverse flow status against long-term averages. Timing varies by year: in dry years the
reversal started late, in July or August in 2019, 2020, and 2023, and on time, in late May, in 2022 and 2025 . The
lake is full in September and October, and operators open it to vessels from about mid-August.

How Does Your Route Change the Best Time?

The route decides which season matters. On the Vietnam leg, water level changes little. On the Cambodian leg, the
Tonle Sap lake decides whether a vessel sails to Siem Reap or hands you to a bus or a flight.

In low water the lake is too shallow for a river vessel, so the Cambodian leg changes and the Vietnam leg does not.
Operators place high water between mid-August and mid-November, and the dates vary each year. Mean lake depth in the
dry season is 1.6–3.3 ft (0.5–1.0 m), against 20–30 ft (6–9 m) at the peak. The table lists
the two low-water plans that operators use on the Saigon to Siem Reap route .

The rows run from the shortest transfer to the longest.

Which Holidays Change the Calendar?

Four holidays move crowds and open hours along the river: Bon Om Touk (23–25 November 2026), Tet (6 February
2027), Khmer New Year (14–16 April 2027), and Bon Om Touk 2027 (date not yet set). The 2027 dates are expected
dates until the Cambodian 2027 sub-decree is read .

Some sites list Bon Om Touk 2026 as 24–26 November. The decree lists 23–25 November, and 24 November,
the full-moon day, falls in the middle.

The rows run in date order.

Which Month Should You Choose?

Choose the month by the one thing you cannot give up: lake access, dry weather, a festival, birds, or green fields.
The table gives a gain and a cost for each goal.

The rows run in calendar order, from January to November.

How Does a Six-Guest Vessel Handle the Water Season?

Calypso Mekong operates one Aquila 44 power catamaran, 44 ft 1 in (13.44 m), with three cabins and up to six
guests, on the Saigon to Siem Reap route only. It sails by day and runs in the flood season, from about mid-August
to December, when the lake is deep enough to cross. Calypso Mekong has a commercial interest in this route, and the
table states each rule beside its status.

The rows run from the season to the daily decision to the lake night.

Questions About the Mekong Cruise Season

The four questions below come up after you choose a month.

Does It Rain All Day in the Green Season?

No. Showers usually come in the afternoon and last about an hour . Ho Chi Minh City records rain on 13 to 19 days a
month from May to October, counting days with 0.1 mm or more, not hours, and the remaining days stay dry. Read What
Does Each Season Look Like on the Water? for each season in turn.

What Does Draught Mean, and Why Does It Matter in Low Water?

Draught is the depth of a vessel below the waterline, measured from the surface to the lowest point of the hull.
The Aquila 44 draws 3 ft 3 in (1.0 m) without skegs and 3 ft 10 in (1.16 m) with them (manufacturer catalogue) , so
a crossing rule of 7 ft 3 in (2.2 m) leaves 3 ft 5 in–3 ft 11 in (1.04–1.20 m) under the hull. The MRC
reports a dry-season mean depth of 1.6–3.3 ft (0.5–1.0 m), so a vessel needs more water than the lake
holds in April; see How
Does a Six-Guest Vessel Handle the Water Season?.

Which Suits a Mekong Cruise Better, High Water or Low Water?

The answer depends on the route: high water opens the lake and Siem Reap by river, while low water brings cooler
nights, drier weather, and, on some lines, a road or air link. Rain runs 9.4–10.7 in (240–273 mm) a
month in September and October, against 2.5 in (63 mm) or less from December to April. Neither wins on every
attribute, and Which
Month Should You Choose? sets each against a goal.

Which Guides Cover Each Part of a Mekong Cruise?

Three groups of pages cover the rest of a Mekong cruise.

The rows run from route planning to the sailings to your data.

When Is the Wrong Time to Cruise the Mekong?

The wrong time is the one that clashes with what you need. Avoid January to mid-August if you want to reach Siem
Reap by river in a vessel that needs high water. Avoid early May to late June if your cruise line pauses. Avoid Tet
week if you want quiet banks and open shops.

The rows run from route to weather to calendar to flights.

Calypso Mekong does not sail in low water. Return to Which
Month Should You Choose? and choose again.