Temperature
White tea wants cool and stable, somewhere around 15 to 25 degrees Celsius. Unlike green tea it does not want a fridge, and the reason is humidity rather than temperature.
A domestic refrigerator is a damp place, and white tea is more porous than it looks. Every time a container goes in and out, it carries the risk of condensation on the leaf, and that is how a promising cake turns musty in a single season.
What white tea actually needs is stability. A spot that stays within a few degrees all year is better than a spot that is colder on average but swings. Consistency is what makes the change predictable.
If you can only optimise one thing, make it this. Temperature, humidity, darkness and container all matter, but a stable room in a plain box will beat an ideal setup in a space that swings.
Humidity
Aim for roughly 50 to 60 percent relative humidity. That is the band where white tea transforms slowly and cleanly, without going sour on the one hand or stalling on the other.
Below about 45 percent, very little happens. The tea will keep perfectly well for years, but it will taste almost the same at the end as at the start, which defeats the point if you were ageing it deliberately.
Above about 70 percent, you are in mould territory. The smell to watch for is a damp, sweet, slightly sour note on the dry leaf. If you catch it early, moving the tea somewhere drier and checking it weekly can save the rest of the cake. If you catch it late, it is finished.
Light and air
Keep it in the dark. Light degrades the aromatics and bleaches the leaf, and both effects are irreversible.
On air, the answer depends on the form. Loose white tea should be sealed, because it has a lot of surface area and picks up odours fast. A cake can be left in its wrapper inside a box or a cupboard, because the compression already limits exchange, and a little air movement is part of how it develops.
Either way, keep it away from anything with a smell. White tea is delicate enough that a cake stored beside a bag of coffee will taste of coffee within a year, and there is no way back from that.
The target environment
The target for white tea is cool, dark, moderately dry, and undisturbed. Sealed tins for loose leaf, wrappers plus a closed box for cakes, and a spot nobody opens very often.
Add a hygrometer to the storage space rather than to the container. What you want to know is the environment, not the microclimate inside one tin, and the room reading is what tells you whether to act.
Then leave it alone. The most common mistake with white tea is checking it every month. Every opening resets the atmosphere inside the container and slows the very process you are waiting for.
Adjust through the year
Seasons shift, and a cupboard that reads 18 degrees in winter can reach the high twenties in summer. That range is survivable, but it does speed up the loss of aroma, so it is worth knowing about.
Recheck the storage spot twice a year. If summer pushes the room above 25 degrees for weeks at a time, move the tea to the coolest interior space you have, which is usually a north-facing room at floor level rather than a high shelf.
The same applies to humidity. Most heated homes get very dry in winter, often below 40 percent, and transformation slows to nothing for those months. That is not harmful, but it does mean a cake in a European flat will age more slowly than the same cake in Fujian.
If you want to narrow that gap, a cabinet with a bowl of water in it will lift the local humidity by a few points for very little effort. Do not put the water inside the tea container. You want to change the room, not wet the leaf.
Also resist the temptation to open cakes more often in a dry winter to check on them. The room being dry is not an emergency, and every opening does more harm than the dryness does.