North vs south Vietnam weather: Hanoi and the Mekong Delta

Month by month

Winter: cool and grey against hot and dry

In January the mean in Hanoi is 16.6°C and in the Mekong Delta 25.4°C. Hanoi gets 22.5 mm of rain over 9.5 rain days, plus 5.2 drizzle days, and 68.7 sun hours. The Mekong Delta gets 10 mm over 2 rain days and 244.9 sun hours. In February the gap is wider: Hanoi has 48.1 sun hours and the Mekong Delta 243.

Hanoi has more rain days than the Mekong Delta from January to April, and fewer from May to December.

The daily range makes the gap clearer. A January day in Hanoi averages a high of 19.8°C and a low of 14.5°C. At Can Tho the January average high is 30.2°C and the low 22.3°C, so the Mekong Delta's coolest nights are warmer than Hanoi's January afternoons. The record lows differ just as much: 5°C at Hanoi, in February, against 14.8°C at Can Tho, in January.

This Vietnam Today report covers a day of intense cold in northern Vietnam.

Summer: Hanoi is the hotter one

From June to September Hanoi is warmer than the Mekong Delta. In July the mean is 29.4°C in Hanoi and 26.9°C in the Mekong Delta. The Mekong Delta's mean stays between 25.4°C and 28.5°C all year, while Hanoi's runs from 16.6°C to 29.4°C.

Hanoi's summer highs average 33.4°C in June and July, against 32°C and 31.4°C at Can Tho. Hanoi also holds the higher record, 41.8°C in June, while Can Tho's is 40°C in April. Summer is storm season in both: Hanoi averages 10.9 thunderstorm days in July and Can Tho 10.6 in May and 10.8 in October.

A second record for Hanoi

The Japan Meteorological Agency publishes monthly normals for Ha Dong, listed at 20.97°N, 105.77°E and 6 m. Its means run a little warmer than the QCVN Hanoi table, at 17.7°C in January and 30.4°C in June, but they show the same winter dip and summer peak. JMA gives no rainfall normals for Ha Dong.

Asked what Vietnam's weather is like in October, one r/VietNam user replied:

"You'll get all kinds of the countries weather during that time in different parts. Warm, sunny, rainy, cold, humid, windy, typhoon!"

u/SpexterZ on r/VietNam

Same rain, different calendar

Hanoi has more rain than the Mekong Delta in every month from January to August. It peaks in August at 309.4 mm. The Mekong Delta has more from September to December and peaks in October at 300.9 mm. Its rain comes on many days: from May to October it has more rain days than Hanoi in every month, 21.5 to 22.1 from July to October.

Humidity follows the rain. Can Tho is most humid in August and September, at 87% and 87.1%, and least humid in March, at 77.9%. Hanoi peaks in April at 84.7% and is driest in December at 76.2%. Drizzle is a northern habit only: Hanoi has 9.4 drizzle days in March, and Can Tho has none in any month.

For the wettest month at the other places, see the rainy season guide, and for the driest, the driest month guide. The November comparison puts both stations next to the rest of the country.

Our take

The north and the south suit different trips in winter. December to February is the Mekong Delta's best stretch, with 3.8 to 41.5 mm of rain and over 215 sun hours a month, while Hanoi is cool, grey and drizzly at the same time. From May to October both are wet, but in different ways: the Mekong Delta has more rain days in every one of those months, and from June to September Hanoi is the hotter of the two. If you only have one trip and want both ends of the country, April and November are the compromise this record supports, with under 140 mm of rain at both stations.

How we checked this

The station figures come from 11 tables of QCVN 02:2022/BXD for Hanoi and Can Tho, and the cross-check from JMA ClimatView's monthly normals for Ha Dong. We matched each value against both sources on 8 October 2026, when we also removed the straight-line distances we had computed ourselves, and checked them again on 24 October 2026. Last reviewed: 24 October 2026.

What this does not tell you

The regulation behind the tables does not state its observation period. "Rain day" is not defined by the source. These are averages, and a particular week can differ. The Hanoi page and Mekong Delta page have the full tables, and the weather by month page shows every place we cover.

References

• QCVN 02:2022/BXD, National technical regulation on natural physical and climatic data for construction: https://datafiles.chinhphu.vn/cpp/files/vbpq/2022/10/02-bxd.pdf. Checked 2026-10-24.
• Japan Meteorological Agency, ClimatView monthly normals, Ha Dong (48825): https://ds.data.jma.go.jp/tcc/tcc/products/climate/climatview/graph_mkhtml_nrm.php?n=48825&y=2026&m=8&e=7&r=1&s=1&k=0. Checked 2026-10-24.

Photo (cover): Andre Hospers / Wikimedia Commons, CC BY 4.0

Data checked: October 2026.