In plants, the circadian system controls a plethora of processes, many with agronomic importance, such as photosynthesis, photoprotection, stomatal opening, and photoperiodic development, as well as molecular processes, such as gene expression. It has been suggested that modifying circadian rhythms may be a means to manipulate crops to develop improved plants for agriculture. However, there is very little information on how the clock influences the performance of crop plants. We used fluorescence measurements to characterize the circadian phenotypes of 50 accession of wild barley (Hordeum vulgare ssp. spontaneum) from widely different ecogeographical locations in the Southern Levant. Via statistical modeling we established a connection between circadian rhythm phenotypes and certain environmental conditions for example, period time seem to be affected by temperature while rhythm amplitude was correlated with soil quality parameters. We also examine how circadian phenotypes change in heat stress conditions as rising global temperatures are rapidly becoming a serious concern. We have managed to establish an interesting connection between plant vitality in heat stress and change in circadian period time and rhythm amplitude. Plants accessions that fared well in heat stress are plants that managed to shorten their period time and maintain a high rhythm amplitude. Our hope is that these connections between environmental parameters, plant vitality and circadian phenotypes will help farmers chose the right accessions to plant in their fields according to the environmental challenges present in their locale.