From KHOU

County Clerk recommends alternative sites as record numbers of early voters continue to swell
Both Monday and Tuesday of this week yielded unprecedented numbers for early voters in Harris County.

The total number of early voters in Harris County as of October 26 was 240,846 with a record high of 46,393 voting that day.

Harris County has now cast more ballots than any other county during the early voting period. If the turnout trend holds, it will have more votes cast in the November 2 Harris County General Election than at any other point in its history. Turnout levels are expected to increase as the early voting deadline nears.

I did notice that Harris got on the ball with it's turnout this week. Historically (and still the case now) it is trailing other counties in the percentage turnout category. As for Hidalgo, it may be a cultural thing, as I know a lot of Hispanics here in Austin like to vote together or on elections day (in addition to Democrats also liking to wait until Election more so than Republicans).