The alpine Paramo of Chingaza National Park, Colombia, has a highly variable cloud regime typical of many tropical alpine areas. Yet, little information is available regarding the effects of such dynamic sunlight regimes on alpine temperatures. A close association between changes in incident sunlight and corresponding air (T-a) and leaf (T-1) temperatures occurred in two dominant species with strongly contrasting leaf form and whole-plant architecture. Spikes in sunlight incidence of >3000 mu mol m(-2) s(-1) occurred during cloud cover and corresponded to increases in T-1 of 4-5 degrees C in a 1-min-interval in both species. Although T-1 was predominately above Ta, during the day, depressions below Ta of over 6 degrees C occurred during cloudy conditions when photosynthetic photon flux density (PFDs) was <400 mu mol m(-2) s(-1). The greatest frequency (69%) of changes in incident sunlight (PFDs; over 2-min intervals) was less than 100 mu mol m(-2) s(-1), although changes >1000 gmol m(-2) s(-1) occurred for 2.4% of the day, including a maximum change of 1512 mu mol m(-2) s(-1). These data may be valuable for predicting the ecophysiological impact of climate warming and associated changes in future cloud regimes experienced by tropical alpine species.