The first place to look for information on sky conditions should be the Houston meteogram from Unisys, which gives you the forecast for Houston over the next 48 hours:
Here is a brief translation of the symbols:

The top graph shows the temperature (top curve) and dew point (bottom curve) plotted against universal time (UT, aka 'Z'). To convert to CST subtract 6 hours. When the dewpoint approaches the temperature we often have fog (symbol '='). Yellow dots mean rain and the funny squiggly symbol is a thunderstorm on the WX line. Predicted precip amounts are in inches for each 3 hr interval. The VIS numbers refer to visibility in miles, of use in aviation.

The circles indicate cloud cover. An open circle is clear, and filled is cloudy. The flags attached to the circle show wind direction (top = north, right=east) and velocity in knots (a full flag equals 10 knots). Usually the dewpoint rises and it gets hazy (but perhaps better seeing) when the wind shifts to the south.

The second graph shows the predicted height of the cloud deck in feet. If only 20000 is indicated this is probably light cirrus that will cover the sky and lower transparency, but may give good seeing. Lower clouds are usually either fronts or the puffy varieties, which you may be able to observe through but beware of sudden showers.

The bottom graph is barometric pressure, not that useful for us.

Additional Weather Links

For a second opinion, try the NOAA meteogram, which has a good graphical layout. Infrared satellite images often show cloud decks well. Try clicking on 'Loop3' or Loop12' to get a movie. Sometimes by looking at a movie you can tell when a front will clear out the clouds. Note the Z-number in the upper left corner. This is the Universal Time of the image. So, for example, 0430Z is 10:30pm CST. Another good source for weather movies is the NCAR Site.

A surface map is also sometimes helpful. In this case the number to the upper left of the cloud cover is the temperature, and the number to the lower left is the dewpoint. The flags are as in the meteogram. High pressure (clockwise circulation) is marked as blue H's, and lows are red L's. Cold fronts are blue, warm fronts red, stationary fronts dashed, occluded fronts in purple, and troughs in dashed yellow. You can even run a movie.

Really(!) clear areas are typically where the water vapor content is low - usually not us :(.

Lots of places give the 5-day forecast. My favorite has a lot of annoying ads but you can get rid of them if you become a member for 5$ a year.

For fun, you might try the Clear Sky Clock (reproduced below), created with observational astronomers in mind. The vertical red lines indicate midnight. The most important constraints for us are the Cloud Cover, Darkness, and Humidity. Deep red color on the Humidity index usually means fog for us. This graphic is nice, but not always reliable! It is always best to check the latest IR images.

                     Latitude    Longitude
Campus             : 29:43:09.6 95:24:15.6
George Observatory : 29:22:30   95:35:37. 
Manvel location    : 29:27:56   95:20:17.7 

Happy Observing!