The total of 2,831 handily surpassed the 2,289 sold in March, the previous best-selling month for the Volt.
But Chevy may not be able to keep up that pace indefinitely.
The end of a host of discount deals could combine with a planned plant shutdown to limit supplies and render the remaining Volts more costly to buyers.
Anton Wahlman, who covers plug-in cars for TheStreet.com, wrote to Green Car Reports earlier this week about what he sees in Silicon Valley, a hotbed of Volt sales.
The super-duper lease/sale promotions for the Volt ended yesterday.
I heard and saw anecdotes saying that Chevy dealers worked overtime this three-day weekend to sell and lease a bazillion of them. Many cleared their Volt inventories down to zero.
And now they won't be getting any more Volts for two weeks or more, in some cases. Those dealers can get cars from other dealers, but otherwise they may be supply-constrained for the rest of the month, and even much of October.
That's because while there are Volts in the distribution pipeline, on September 17, Chevrolet will suspend production at the Detroit-Hamtramck assembly plant for four weeks.
This will allow the company to install tooling so the plant can build 2014 Chevy Impala sedans as well as the Volt and the 2013 Malibu now made there.
Wahlman suggests that September sales of the Volt may be closer to 1,500 than 3,000. He continues:
I have multiple neighbors who picked up Volts in the recent days; I think one guy even got two of them. At $199 a month plus tax, with almost nothing down, why not? I wonder when those kinds of deals will return.
Wahlman did note that it's possible that the strong Volt sales are limited to California. (GM has said sales were strong in Michigan too.)
California buyers account for roughly one-third of all Volt sales.
Now that recent 2012 Volts--and the updated 2013 Volt--are eligible for the coveted "green sticker" that gives the cars access to the High Occupancy Vehicle (HOV) lane with just a single occupant, the Volt should continue to sell better until all 40,000 of those stickers are assigned.
The car, of course, is far from the only one eligible for those stickers. Others include the Toyota Prius Plug-In Hybrid, the Honda Accord Plug-In Hybrid that will arrive early next year, and upcoming Energi plug-in hybrid versions of the Ford C-Max hatchback and Ford Fusion sedan.