Marshall High School, Ridge Point High School, Schiff Elementary School and Quail Valley Elementary School are all affected.
School officials say the air conditioning has been repaired at Marshall High School. Fort Bend ISD anticipates the building will be cool for classes on Wednesday.
There are still issues at the three other schools.
According to the Fort Bend ISD website, maintenance crews have been working through the night to fix the problems.
The last day of classes at Marshall High School is May 31.