We had a similar question to this, way back in June 2008 from someone planning a reunion. Being terminally lazy, we are recopying it here, and will make corrections to any of the links we previously mentioned.
Gee, ask us an easy one, like how to have world peace. Or cheap gasoline. Nature is a law unto itself, and predictions are risky, to say the least. Officially, the peak bloom of bluebonnets in Central Texas is in mid-April. They are winter annuals, with the first green rosettes appearing in January, and earliest blooms sometimes in late February. As you no doubt know, 2007 was a banner year for bluebonnets, with rains the previous Fall and again in the late Winter and early Spring, all just the right time. We had a moist, cool Spring and early Summer, and the blooms not only started early, they were profuse and lingered late. In 2008, they seemed to vanish. West of Austin, there was so little rain that wildflowers were few and far between, with bluebonnets not even appearing in many places. In Austin, it wasn't much better, and we were recommending that people wanting to see fields of blue should go east toward Brenham, but even there, they felt the unsatisfactory conditions. Since we have been in an extreme drought in Central Texas for more than a year, we fear that the results are going to be much the same. Possibly, if we get some substantial rains soon, some of the season might be saved, but bluebonnets really depend on Fall rains and a period of cold winter to develop and germinate.
The Wildflower Center website always has information on what's blooming, and will have bluebonnet forecasts in the Spring. Several other groups provide information on sightings and routes for viewing wildflowers. One of these is Lonestar Internet, Inc. You can find more routes and information at the Texas Hill Country Wildflower Trail web site. DeWitt County offers its own wildflower site as does Brenham, Texas in Washington County. On the Brenham page, select "Visitor Information", then "Nature Watch" to find their information on wildflowers. We went in and checked all these sites, and it is apparently too early for anyone to be predicting; everyone is in the same predicament we are, as in "who knows?" Keep checking those sites, and as the situation develops, there will start being more specific information, hopefully, information that the bluebonnets have miraculously pulled a great blooming season out of their hats.