Problem
High temperatures and humidity can play havoc with sourdough starters and breads.
Explanation
Yeasts and bacteria work faster the warmer it gets – up to about 35°C when their activity starts to suffer due to excess heat. In general, the warmer it is, the quicker a sourdough will ferment. There are three ways to deal with this problem:
Use cold water to refresh your sourdough and keep it in a cool place, possibly in the fridge for some of the time. It’s difficult to be prescriptive about time and temperature because situations vary, but try to keep the dough below 27°C.
Reduce the duration of any refreshment stage. For example, if a normal refreshment of a wheat sourdough is 4 hours, in very warm weather this might be reduced to 2½ hours.
Make both the starter and your production sourdoughs stiffer, i.e. reduce the water content. This will slow down the fermentation, but will tend eventually to produce more acetic acid, giving a more vinegary taste to your bread. To limit this effect, do not chill your dough, for instance by refrigerating it for a long proof.
You can use one or all of these levers to adjust your method to warm weather. The humidity of the tropics means that you may need to use a bit less water than the recipe says. But most recipes prescribe too little water anyway, so this is unlikely to be a big issue.