March in Hat Yai, Thailand, brings average daily highs of 33°C and overnight lows of 24°C in the 2016–2025 historical record. Allow room to shorten long outdoor plans when the day's forecast is hotter than you want. A schedule with easy breaks and less travelling between stops will give you more choices.
In the record, at least 1 mm of rain or snow falls on 10 of 31 days on average, a daily chance of 31%. 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 11 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.
If food is a reason for the trip, leave time around meals rather than filling every gap with another journey. Check the places you choose for current opening hours. For time in town, cluster a few stops together and leave the rest of the day open. Check transport and opening hours for any plans that run late.
April has an average daily high of 34°C, 1°C higher than March. Its historical rain-day chance is 61%, compared with 31% 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.