No, ‘thought storms’ often arise at any time, like weather patterns in the mind. The only reason they’re more noticeable in meditation is because you’re not distracted by anything else …
What drives a thought storm is an emotion of some kind .. where the hormonal energy of an emotion electrifies a set of thoughts or a memory, causing it to attract other thoughts and memories that are ‘in kind’ so to speak – and you get a thought storm.
So at those times, don’t bother with the thoughts … don’t bother noting them or the memory. By the time they’ve become a thought storm, its a different story to the usual …they’re being driven by something deeper – so that is where you must go to deal with what’s happening. So let the thoughts scream and wail and natter and instead, focus on where they are all coming from … the emotion.
Plunge your attention deep into the feelings, the sensations, the body reaction – and keep it there … keep bringing it back, exploring the physicality of what is happenng
Once the feeling has been ‘known’ or ‘witnessed’ in this way, it will dissipate.
And as it dissipates, so too will the thoughts it created.
Hope that helps,