Dissapointed

My seedlings have not been doing well.  The arugula and radishes are the only 2 items doing OK.  My cilantro has just started to peek out of the soil.  But the other 8 varieties of lettuce have done absolutely nothing.  I was planning on replanting today but for the next 5-7 days we are going back into the high 80s and 90s.  Being my first year for Fall crops I was excited but nothing will grow in this heat!