Climate change and abiotic stress factors are the key players in crop losses around the globe. Among the different stresses, extreme temperatures (heat and cold) disturb plant growth and development, reduces productivity, and in severe cases, leads to plant death. The plants have developed numerous strategies to safeguard themselves against the detrimental impact of temperature stress. Exposure to stress evokes the accumulation of various metabolites like sugars, sugar alcohols, organic acids, and amino acids. Plants accumulate the amino acid proline (Pro) in response to several abiotic stresses, including temperature stress. Proline abundance may result from de novo synthesis, hydrolysis of proteins, and reduced utilization or degradation. Pro also imparts stress tolerance by maintaining the osmotic balance (still controversial), cell turgidity, and indirectly modulating the metabolism of reactive oxygen species (ROS). Furthermore, the crosstalk of Pro with other osmoprotectants and signaling molecules like glycine betaine, abscisic acid, nitric oxide, hydrogen sulfide, soluble sugars, etc., helps in strengthening the protective mechanism under stressful environments. The development of temperature-smart cultivars can be achieved by manipulating the biosynthesis of Pro through genetic engineering. Therefore, this review presented an overview of plant responses to extreme temperatures and an outline of the Pro metabolism under extreme temperatures. The exogenous application of Pro as a "shield molecule" under extreme temperatures is also presented. Proline crosstalk and interaction with other molecules have also been discussed. Finally, the potential of genetic engineering of Pro-related genes has been explained to develop temperature-smart plants. In short, we conclude that exogenous application of Pro and genetic engineering of Pro genes promise ways forward for developing temperature-smart future crop plants. It is proposed various approaches can be adopted to increase Pro levels in "temperature-smart plants" to combat the impending crisis of climate change.