Yep, EPA probably switched over to summer fuel. Check the 'state summer RVP standards' for specific RVP limits where you live.
The Oil Drum | Refining 101: Winter Gasoline
Volatility/Reid Vapor Pressure (RVP) | Fuels and Fuel Additives | US EPA
Regulations and Standards | Fuels and Fuel Additives | US EPA
Phase IV RVP regulations was proposed in Caly a while back, thank goodness it was never implemented (caly regs tend to trickle down to the rest of the US after enough time has passed) or it would've been the death of most carbureted engines, but then thats why Sunoco is still around.
one reason companies are using 10% or a specified volume of ethanol is the RVP can be raised further (in many places in the US, not all)