Take a look at my spreadsheets. In them I compare the percentage of the vote each party got in 2012 to 2016 and 2014 to 2016 in seats where a Republican and a Democrat ran against each other in an election.
here were 33 congressional seats where that had a Democrats and a Republican in both 2012 and 2014. In 2012 Democrats got 57.1% of the vote in 2014 they got 53.9%. There was a slightly different group of congressional districts that had a Democrat and a Republican in 2014 and 2016. In 2014 Democrats got 53.3% of the vote in them. In 2016 they got 58.9%. For good measure we can compare the 35 congressional seats with both a Democrat and a Republican in 2012 and 2016. In 2012 Democrats got 56.0% in these seats. In 2016 they got 58.2%. The swings from 2012 to 2014 and then in the other direction in 2016 were dramatic.
These swings didn't result in seats flipping, however, because the seats which had the biggest shift from 2012 to 2014 weren't ones that were close in 2012. Republicans lost 7 congressional districts by 5 points or less in 2014. Since Republicans didn't take these districts in 2014 they couldn't flip back to the Democrats in 2016. The seats Republicans did win in 2014 were mostly one sided. Democrats lost all of them by 12 points or more. So even a big shift in 2016 didn't result in any of these districts flipping.
Democrats are certain to do much better in 2018 than they did in 2014 and may even do better than they did in 2016, the best year they've had this decade. If they do that might result in a dramatic number of seats flipping, but it also might not. Mimi Walters won by 17 points in 2016. David Valadao won by 13 points. Ed Royce won by 14. The shift could be big enough where these seats flip, but it also could be big and these seats won't. If there is a wave, it won't miss California. Because it hasn't in other elections.