Acevedo made his move with 500m to go of the 5.9km final ascent in blistering heat to secure the win by a margin of 12 seconds from race favourite van Garderen.
The stage win gives the Colombian the overall lead with a 12-second advantage over van Garderen and 27 on Irishman Deignan.
The early escapees were Pat McCarty (Bissell), Ben Jacques-Maynes (Jamis-Hagens Berman), Scott Zwizanski (Optum) and Sylvain Chavanel (Omega Pharma-Quickstep) - with the peloton coming across the first climb, Mountain Center, 9:30 down - but a combined effort between 5-Hour Energy and UnitedHealthcare whittled their advantage down to 1:30 with less than 10km to go.
Deignan attacked and had the lead with 2km remaining before being caught by van Garderen but Acevedo managed to hold the American’s wheel before assuming the lead in the last 500m in 50C (122F) heat.
"[Acevedo] he was super strong out there. When he attacked I was too afraid to go into the red because in this heat if you go into the red just a little bit you just can't recover. I made a little bit of a gamble to stay in my tempo and claw him back but he was definitely strong enough to hold on,” said van Garderen.
"He got the stage, and good on him, but I feel confident for the time trial, and I think I'm in a perfect position for the overall classification."