The 1985 Puerto Rico floods produced showers and thunderstorms across the island and the deadliest single landslide on record in North America, that killed at least 130 people in the Mameyes neighborhood of barrio Portugués Urbano in Ponce.

The system moved into the Caribbean Sea on October 5 and produced heavy rains across Puerto Rico, peaking at 31.67 in (804 mm) in Toro Negro State Forest.

In addition to the deadly landslide in Mameyes, the floods washed out a bridge in Santa Isabel that killed several people.

Moving westward, the system entered the eastern Caribbean Sea on October 5,[3] although rainfall began spreading across Puerto Rico the day prior.

[6] The intense rainfall triggered the landslide, although pre-existing conditions such as a leaking water main and poor sewage flow likely contributed to the event.

[10] On October 7, Puerto Rico's governor Rafael Hernández Colón declared an islandwide state of emergency and activated 300 National Guardsmen to assist in search and rescue operations.

[10][15] The United States Coast Guard flew helicopters into flooded areas to rescue stranded residents, including 18 people along a hill in the western portion of the island.

[16] After the storm, the Puerto Rico's government created a Rainfall-Runoff Alert Network, designed to predict flash flooding in advance, in conjunction with the National Weather Service, the United States Geological Survey, and the territory's Department of Natural Resources.

[17] On October 10, United States president Ronald Reagan declared 33 municipalities across Puerto Rico as disaster area.

[20] Initially, a death toll of 500 people was reported, although that was "the product of the original, collective hysteria," according to the mayor of Ponce's press officer.

Additionally, the number of destroyed houses was overestimated, only to be revised downward owing to before-and-after satellite images and interviews with survivors.

[21] After the Mameyes landslide, about 150 people, including National Guardsmen, worked to locate bodies with the assistance of six rescue dogs.

[23] Workers initially had difficulty assisting the affected families due to the occurrence in early morning and the continued intensity of the rain, and as a result, only 50 bodies were recovered.

Three days before the Mameyes landslide, a group of children from a nearby Head Start school were asked by their teacher to draw "whatever came to their minds".

The drawings were handed by an unidentified teacher to Gladys Torres, administrator of public documents and Director of the Historic Archive of Ponce.