In the Eastern Pacific, Tropical Depression Eleven-E, along with moisture from a monsoonal flow, brought torrential rains to southern Mexico and Guatemala. At least 84 people were killed in the two countries and damage exceeded $500 million. In northern Mexico, the effects of Tropical Storm Hermine were limited. Further north, severe flooding affected large parts of Texas and Oklahoma, killing eight people and leaving at least $240 million in losses.
In August 2010, a tropical wave in the eastern Atlantic contributed to the formation of Hurricane Danielle; Danielle eventually tracked west and then northward before dissipating south of Newfoundland after ten days. However, the southern portion of the disturbance became disassociated with Danielle's development and tracked west into Northern South America, reaching the East Pacific on August 29. Thunderstorm activity was confined over Central America until September 2, when showers developed over and around the Gulf of Tehuantepec. The National Hurricane Center (NHC) first assessed a low probability of tropical cyclogenesis at 00:00 UTC the following day.
Throughout September 3, the disturbance quickly developed in the gulf before a wind circulation at the surface beneath the system was detected; thus, the NHC designated the developing system as a tropical depression at 18:00 UTC that day when the storm was 115 mi (185 km) southeast of Salina Cruz, Mexico. Following formation, Eleven-E moved slowly towards the northwest and developed a well-pronounced inner rainband late on September 3. At 06:00 UTC the next day, the depression peaked with winds of 35 mph (55 km/h) before making landfall an hour later east of Salina Cruz. The cyclone's organized appearance on radar, which included a developing primordial eye, suggested that the depression was near tropical storm intensity at the time of landfall. A ship documented tropical storm-force winds during this period, but as they were well removed from the storm, its is believed that these stronger winds were associated with a nearby monsoonal wind flow. After moving inland, the depression quickly deteriorated and became a remnant low-pressure area by 18:00 UTC on September 4 over the Isthmus of Tehuantepec.
Though the mountainous terrain of Oaxaca and Chiapas greatly disrupted Tropical Depression Eleven-E's organization and led to its demise, the former cyclone's mid- and lower-level circulations remained intact as they moved into the Bay of Campeche. New and intense convection arose as soon as the vortex moved back over open water on September 4, hours after Eleven-E's declassification. Over the next day, the area of thunderstorms, initially disorganized, coalesced into a tropical depression once again in the southern Bay of Campeche at 18:00 UTC on September 5. Twelve hours after formation, the NHC upgraded the system to tropical storm status following conclusive reports from a nearby buoy. As a result, the tropical cyclone was named Hermine. Steady intensification continued as Hermine gravitated towards the Texas-Mexico border. Thunderstorm activity increased during the morning of September 6 as they continued to wrap around the center of the storm. Later that day, an eye was detected using radar imagery based in Brownsville, Texas, though the storms surrounding it remained rather meager.
At 02:00 UTC on September 7, Hermine made landfall near Matamoros, Mexico with maximum sustained winds of 70 mph (110 km/h) and a minimum barometric pressure of 989 mbar (hPa; 29.21 inHg); this was the cyclone's peak intensity. After moving ashore, Hermine slowly weakened and moved northward into Texas. At 00:00 UTC on September 8, the weakening tropical cyclone degenerated to tropical depression strength near Mason, Texas. However, Hermine's gusts remained much stronger than its sustained winds. Shortly after the downgrade, the NHC transferred its cyclone monitoring responsibilities to the Hydrometeorological Prediction Center (HPC). By that time, the weakening storm had lost most of its tropical cyclone characteristics, with a long line of thunderstorms extending southwards and paralleling Interstate 35. Hermine was determined to have weakened to a remnant low-pressure area over Oklahoma at 18:00 UTC on September 9, before dissipating over Kansas on the next day.