March in Long Bien, Vietnam, brings average daily highs of 25°C and overnight lows of 20°C in the 2016–2025 historical record. Light clothing is a useful starting point, with room in the plan to pause indoors. Decide how much walking to fit into each day using the local forecast, rather than treating the monthly average as a limit.
In the record, at least 1 mm of rain or snow falls on 10 of 31 days on average, a daily chance of 33%. Leave some freedom to swap an outdoor day with a sheltered one. There is no need to read the average as a fixed number of lost days; it says nothing about how long rain lasts on each occasion.
The calculated day length, sunrise to sunset, averages about 12 hours. Sunshine averages 5 hours a day. Use the daylight window to plan the length of excursions, and check local sunrise and sunset times for the dates of your stay. Sunshine is a separate measure, and those hours need not arrive in one uninterrupted stretch.
Start with the places you most want to visit, then keep the order flexible enough to suit the weather. Check current opening hours and local transport before fixing long day trips. The climate record can help with pacing and packing, but it does not describe what is open during your stay.
April has an average daily high of 29°C, 4°C higher than March. Its historical rain-day chance is 37%, compared with 33% this month. If your dates are flexible, compare those trade-offs with the kind of days you want. Neither set of averages predicts the conditions of one particular holiday.