Hose, 24, played 31 games for Somerset, having joined them in 2015, making his maiden one-day hundred in May.
He also made a match-winning 59 off just 28 balls in Somerset's T20 Blast victory over Middlesex on 16 July.
"It's a fantastic opportunity at an exciting time for the club. I now just need to work hard, score runs and earn a first-team place," Hose told BBC WM.
"It was hard leaving Somerset but I went with my gut feeling. You just get the idea that this club is building something here."
On top of Olly Stone's winter switch from Northamptonshire, Hose's arrival follows last month's signing of former England Under-19s captain Will Rhodes from Yorkshire on a two-year deal, starting in 2018.
"We need to be looking towards the next generation," Bears sport director Ashley Giles told BBC WM.
"We've been through this cycle before. It was a big part of my coming back to the club. We've had some pain. We might have a bit more yet. But we just need to make sure we have the right people on the bus."
Isle of Wight-born Hose came through the Hampshire development programme before joining the MCC Young Cricketers prior to his move to Somerset.
He will be available to make his Bears debut in Friday night's T20 Blast match against Yorkshire at Edgbaston and for the rest of this year's competition.
But he will not be allowed to figure in Championship cricket for Warwickshire this season until the the fate of the Bears and fellow relegation candidates Somerset is known.
Warwickshire have signed Somerset batsman Adam Hose, who has joined the club immediately on a three-year deal.