The rainy season in Costa Rica normally runs from May to November, coinciding with the hurricane season in the Caribbean. Flooding can occur and heavy rains or hurricanes can cause landslides.
Earthquakes and volcanic eruptions
Costa Rica experiences regular seismic activity. The last major earthquake occurred in September 2012 near the Pacific coastal area of Nicoya Peninsula and measured 7.6. The US Federal Emergency Management Agency website has advice about what to do before, during and after an earthquake or tsunami.
Costa Rica has 16 volcanoes, several of which are considered active. The possibility of eruptions always exists. Several volcanoes are currently active.