If my time parenting two toddlers has taught me anything, it's that toddler tantrums are as unpredictable as the toddler themselves. Sometimes there's a calm before the inevitable storm that follows me denying a request for more ice cream. Other times, their meltdowns have a build up period that rivals a war scene from Braveheart — war paint and all. Although its impossible to truly avoid tantrums altogether, learning the reasons for toddler tantrums (looming, eminent, impending are all appropriate verbs as well,) can help save your sanity and your child's pent up energy for something more useful.
Granted, every toddler is different and "melt down triggers" will be different from one child to the next. My youngest daughter — the one who insists on thanking me for everything, from changing her diaper to lying her down at night — has meltdowns when she's overly tired. The word "no" is a warning to be heeded, and I rarely have problems with her listening. On the other hand, my older daughter is a force to be reckoned with. "No" is an encouragement to push further and tantrums happen on the regular, even with boundaries in place.
Although age and temperament play a huge role in how to handle your child's tantrums, knowing why they happen can help you prevent them altogether or at least know how to better handle them once the storm hits.