December in Quảng Ngãi, Vietnam, brings average daily highs of 26°C and overnight lows of 22°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 25 of 31 days on average, a daily chance of 79%. Make flexibility part of the trip from the outset. Keep time outside easy to rearrange and choose plans that still work if it rains. The monthly figures do not establish whether rain is brief, prolonged or concentrated at a particular time.
The calculated day length, sunrise to sunset, averages about 11 hours. Sunshine averages 6 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.
For a culture-focused visit, group the places you want to see into manageable areas, with time between stops. Check each venue's opening dates before fixing the order.
The following month, January, has a similar average daily high of 26°C. Its historical rain-day chance is 62%, compared with 79% 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.