The fourth named storm of the 2021 Pacific hurricane season, Dolores developed from a low-pressure area that formed offshore the Mexican state of Oaxaca on June 16, 2021.

The storm reached its peak intensity around 15:00 UTC June 19 with maximum sustained winds of 115 km/h (70 mph) and a minimum barometric pressure of 29.2 inHg (989 mbar), just below hurricane strength.

A separate tropical wave crossing Central America around this time interacted with the trough, resulting in a broad atmospheric circulation forming over the region by June 12.

[3] Expanding deep convection over the center of the depression, as well as increasing Dvorak classifications, resulted in its upgrade to a tropical storm at 15:00 UTC, where upon it was named Dolores.

[4] A large tropical storm, Dolores gradually intensified due to favorable environmental conditions for the remainder of the day, characterized by warm sea surface temperatures and low wind shear.

[5] Deep convection began to develop in more organized, large rainbands over Dolores' circulation around 09:00 UTC on June 19, and increased in coverage near the storm's center.

The storm reached peak intensity shortly before 15:00 UTC that day, with maximum 1-minute sustained winds of 115 km/h (70 mph) and a minimum barometric pressure of 29.2 inHg (989 mbar).

[1] The resort city of Puerto Vallarta opened 20 shelters in advance of Dolores due to expected heavy rainfall of up to 380 millimetres (15 in) and anticipated storm surge.

[11] Residents of several states in southwestern Mexico were advised to prepare for tropical-storm-force winds, power outages, landslides, overflowing rivers and widespread punctual rains as Dolores approached.

[17] In neighboring Oaxaca, at least ten communities of the indigenous Zapotec peoples experienced overflowing streams and rivers, as well as damage to agriculture and infrastructure due to the combined effects of Dolores' and Claudette's precursor system.

The worst damage in Oaxaca occurred in the Sierra Sur and Costa regions, where debris were strewn across roads and extensive mudslides rendered many streets impassable.

[27] The Mexican Secretary of National Defense, Luis Cresencio Sandoval, activated Plan DN-III-E following Dolores' landfall, which allowed for the dispatch of 2,302 military units to assist in relief efforts in Colima, Michoacán and Guerrero.