President Luis Arce said about 380,000 families have been affected by the calamity in all nine of Bolivia's departments.
The state of emergency will allow the government to mobilise more emergency personnel for rescue operations and to speed up the purchase of equipment.
Bolivia's rainy season runs from November to April and last year claimed 55 lives.
The Alliance for Global Water Adaptation, an NGO that advises on policy, said in a report last year that "climate change is intensifying Bolivia's water vulnerabilities... increasing the frequency and severity of droughts and floods."
The country is also battling a crippling fuel shortage and has been in a deep economic rut since 2023.
