Hello! It’s very important to keep hydrated. For most adults that is drinking 6-8 cups of water daily, and more if you are engaged in physical activity or manual labor causing sweat. As far as vapor goes, I typically recommend to use dry leaf vaporizers over vapor concentrates. If you do prefer vapor concentrates, try using products that are as clean as possible without harsh chemicals that are sometimes used in the extraction process. Choose products that have been laboratory tested to ensure they are free of toxins, pesticides, molds, and other harmful substances. Choose unflavored vapor concentrates. If after this you still experience headaches, you may want to consider switching to another form of cannabis such as sublingual tinctures or low dose edibles. Best of luck!
Nighttime headaches have many possible causes, and dehydration is not high on the list. Cannabis can cause dry mouth, an effect that is commonly reported, but this is not a manifestation of dehydration. The same amount of fluid is still in the circulation, it’s just that less saliva is being released. If you only experience the headaches after vaping, I would have some concern about that pattern and switch to another method of taking cannabis. If the headaches persist, continue after discontinuing cannabis, or particularly if headache is present in the morning on awakening, I’d recommend further medical evaluation to make sure it isn’t something requiring a different intervention.