River deltas are among the most dynamic and vulnerable ecosystems on Earth, shaped by the delicate balance between sediment supply, hydrological regimes, and marine processes. Nevertheless, they are increasingly threatened by climate change and human interventions. This study presents a comparative analysis of two contrasting Iranian deltas: the humid Sefidrud delta along the Caspian Sea (northern Iran) and the arid-semiarid Arvandrud (Shatt al-Arab) in the Persian Gulf region (southern Iran). Despite extensive research on individual deltas, comparative analyses between humid and arid systems remain limited. However, these deltas face growing threats from climate change and human activities. Therefore, this chapter examines how rainfall regimes affect delta evolution, vegetation, and land surface temperature (LST), and how climate adaptation strategies should be tailored to contrasting hydroclimatic conditions. A key goal is to understand how these macroclimate changes occur and change the local microclimate, especially LST and moisture, which ultimately affect ecosystem functioning and agricultural productivity. Using seven decades of hydroclimatic records (1951–2020) combined with multi-decadal satellite observations (Landsat, Sentinel-2), investigated precipitation trends, LST, and normalized difference vegetation index (NDVI). The results showed that Sefidrud delta exhibits a bimodal precipitation pattern with significant increases in winter–spring precipitation, enhanced interannual variability, rising LST, and declining vegetation cover. This decline in vegetation feedbacks into microclimate conditions, leading to elevated LST and reducing evaporative cooling, thereby intensifying local warming and aridity. The Arvandrud delta illustrated a unimodal winter-only regime with no significant long-term trend in totals but with sporadic extreme events, moderate LST rise, and marked agricultural expansion. While this expansion alters the microclimate by modifying surface properties, its sustainability is threatened by rising LST and water scarcity. Satellite data evidence highlighted profound environmental change, sediment loss, and wetland degradation in the Sefidrud, and rapid agricultural expansion in the Arvandrud, each reflecting distinct human environment interactions. Both deltas, however, exhibit accelerating warming trends, where increasing LST threatens water resources, agriculture, and ecological stability. This comparative analysis highlighted contrasting hydroclimatic trajectories in humid versus arid deltas, the role of anthropogenic interventions in amplifying vulnerability, and the urgent need for delta-specific adaptation strategies under accelerating climate change. Given the limited studies in two important deltas of Iran, it is suggested that future studies on soil-microclimate interactions in diverse delta environments and practical insights for reducing climate impacts and increasing the resilience of delta ecosystems should be conducted.