First brew, crazy ferment

[cletusdog]

I'm brewing an IPA and Saturday afternoon I pitched the yeast. I stored it in a bathtub with a bit of a pool to keep it cool (it's been 100 deg. here all week.)
When I woke up Sunday morning, fermentation had begun. By noon, it was going crazy in the blowoff tube. By Sunday evening it was a really heavy ferment.
When I checked it Mon morning, nothing. There has been no more activity. I agitated it a couple times, but still nothing?

What gives? Less than a day and a half and fermentation is done?

[Ozwald]

I'm brewing an IPA and Saturday afternoon, I pitched the yeast. I stored it in a bathtub with a bit of a pool to keep it cool (it's been 100 deg. here all week.
When I woke up Sunday morning, fermentation had begun. By noon, it was going crazy and by sunday evening it was a really heavy ferment.
When I checked it Mon morning, nothing. There has been no more activity. I agitated it a couple times, but still nothing?

What give? less than a day and a half and fermentation is done?

Check your gravity, it might be done or close to it. There's a few variables you left out of your post like temps, measured OG, strain of yeast, etc. With that hot of an ambient temp you'd almost have to keep a wet towel/shirt over the vessel with a fan blowing on it to keep it down into the yeast's happy range. The tub might have knocked a little temp off, but likely not enough. An extremely aggressive ferment also points to that. Being your first brew, it might be a little tough to gauge, having nothing to compare it to.

Get it as cool as possible (down in the upper 60's, low 70's if you can), watch the gravity to determine if it's done or stuck. If you conclude it's done, I'd personally still wait another day or two before packaging.