My 7 yo son sometimes has "meltdowns" that are (when I take the time to analyze it) triggered by circumstance (hungry, certain foods, tired, sick, feeling ignored) and can easily escalate unless I keep my cool which isn't always easy. They do usually occur at certain times of day so you start to recognize a pattern and pro-actively avoid letting those things happen (make after-school snack, limit sugary foods, have some "down-time", spend some quality time.
I've found that the feeling ignored is usually the biggest trigger in our household. We try to do daily/nightly activities with our son, but sometimes we're busy or tired or hungry or sick. Quality time is key. And a meltdown is a good way to get your attention.
The important and hardest thing to remember is to keep your cool. If you yell, he's going to yell. You and your husband need to decide on an appropriate way to deal and discipline. If you guys are arguing, then your son is in control -- and he's getting the attention he may be craving, even if it's negative. This is what we do. It's usually successful, but sometimes needs to be adapted or updated. Do not argue or yell. Speak slowly and in a low, tone. Although he's too old for time-out, sitting out (I usually make my son sit in a certain place, not his room) until he can get hold of himself is crucial. Do not pay attention to any of the crying/yelling. Tell him why he is sitting out and you will come talk to him when he calms down. Walk away and keep yourself busy. When he calms down, explain to him why he had to sit out and that his behavior is unacceptable. Have him apologize and then let it go. Distract him with a snack or an activity. If he's argumentative, tell him you'll be back when he can calm down and listen without talking back, walk away again. Keep it up until he gives, which he will.
Trying to impose heavy discipline when a child is out of control just seems to make it worse. If he's done something that absolutely demands discipline afterwards (not just a tantrum, but an unacceptable action as well), after he's controlled and has apologized, calmly explain to him that he's lost whatever privilege works best on him and then let it go. Do not harp on the tantrum after. Do not let him argue about it either! Then you're just back to square one and have to start all over again! Be patient, firm and calm -- even when you want to scream and run.