Boris caused heavy flooding in southern Mexico that resulted in ten fatalities; however, a damage estimate is unknown.

The first signs of a circulation on satellite imagery appeared on June 26, centered about 250 miles (400 km) south of the Gulf of Tehuantepec.

In the same advisory, it was noted that the outer rain bands of Tropical Depression Four-E had moved onshore Mexico.

The tropical cyclone moved northwestward at 8 to 10 knots, and for the next two days its maximum sustained winds strengthened from 30 to 75 miles per hour (48 to 121 km/h).

A ragged eye appeared on satellite imagery just before landfall on the afternoon of June 29, at a peak intensity of 90 miles per hour (140 km/h).

Shortly after landfall, Boris weakened to a depression and turned southwestward in response to a building subtropical ridge to its north.

[1] The system, thoroughly disrupted by the mountainous terrain of Mexico, dissipated on the July 1 after moving back over water just south of Puerto Vallarta.

[1] As Hurricane Boris was approaching Mexico, a tropical storm watch was issued for the coast between Manzanillo and Puerto Escondido on June 28.

[9] On July 18, President Zedillo held meetings with the victims of Boris and Cristina, a later storm in the same season, in Tecpan and Acapulco.