In a number of emerging streaming applications, the data values that are produced have an associated time interval for which they are valid. A useful computation over such streaming data sets is to produce a continuous and valid skyline summary. To the best of our knowledge, this problem has not been addressed before. In this paper we introduce an operator called the continuous time-interval skyline operator for evaluating this computation. We also present a new algorithm called LookOut for evaluating the continuous time-interval skyline efficiently, and empirically demonstrate the scalability of this algorithm.