Actually, bluebonnets bloom for a short time, maybe three week early in the 
Houston Spring, in March, after heavy Spring rains have gone on for a bit, 
and when the temperature is in the 60's to 70's.  They would get fried and 
fade in the heat of a Houston summer.  However, I don't know the temperatures 
and rain condition of your summers, and what time of your year would 
replicate those conditions.