Temperatures vary by altitude with the warmest places being in the Brahmaputra and Barak River plains and the coldest at the highest altitudes. It is also influenced by proximity to the sea with the valleys and western areas being close to the sea, which moderates temperatures. Generally, temperatures in the hilly and mountainous areas are generally lower than the plains which lie at a lower altitude. Summer temperatures tend to be more uniform than winter temperatures due to high cloud cover and humidity.