As the Amazon Basin is largely rain forest, you can expect it to be hot and wet for most of the year. Heavy rains are common December through May and it isn't unusual to encounter unrelenting downpours in the summer months. The drier period between May and October sees less rain on average and might be a more pleasant time to undertake jungle treks and river boat tours. There is also a chance you'll experience the unpredictable surazo, a bitter wind blowing from the Argentine pampas and Patagonia, which can create a drastic drop in temperature and result in frost in even the hottest parts of the jungle.
Here are some related tips to help plan your trip to The Amazon Basin: When To Go, Safety, Amazon Basin History, Safety, San Ignacio de Moxos Festival, Getting To and Away from PN Noel Kempff Mercado, Safety, When To Go, San Ignacio de Moxos History and Amazon Basin Highlights.