Hard brown sugar. Here is a cure for hard brown sugar
Place a slice of apple in hardened brown sugar to soften it back up so you can measure it easily and use it often.
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In humid climates, brown sugar often gets hard as a rock. You can put that brown sugar in the microwave for just a few minutes on low so you can use it easily.
Putting your brown sugar in a container with a lid and adding a slice of bread your brown sugar will stay soft so you can use it easily.
If you use brown sugar only on special occasions you can put it in a container and put it in the freezer or in the fridge to keep it fresher for many more months than in the cupboard.