We will be unseasonably warm through Wednesday with highs in the upper 70's and low 80's (the normal high is 70). Until I see a well defined frontal boundary enter northern Oklahoma and the Texas panhandle it it will be difficult to say exactly when the front will usher the colder air into the Houston area. For now, I'm going with 'mid-day' Thursday timing on the front passing through downtown Houston... but it could be much earlier or later in the day.
Here's a look at where the cold air is right now. When the front does get here we will quickly drop from the 70's into the 40's with a gusty north wind.