The depression slowly intensified, and reached tropical storm intensity the following day, before subsequently making its first landfall on the Yucatán Peninsula.

Under favorable conditions for tropical cyclogenesis, Stan attained hurricane strength on October 4, and later reached peak intensity with winds of 80 mph (130 km/h) and a minimum barometric pressure of 977 mbar (28.9 inHg).

Due to Stan's position within a large area of convective activity and thunderstorms, the hurricane's effects were far-reaching and widespread across Central America.

The Santa Ana Volcano erupted while Stan was producing heavy rains in the country, which contributed to the damage already wrought by mudslides.

[1][3] The system's organization fluctuated, developing a weak circulation and broad low-pressure area on September 28 over the western Caribbean Sea.

[3][4] The Hurricane Hunters flew into the system on September 29, observing a broad area of thunderstorms with insufficient organization to be classified a tropical cyclone.

[5] Over several days, the system failed to consolidate and was "slowly festering", as described by NHC forecaster Stacy Stewart.

The associated convection developed outflow as the overall system moved generally westward, steered by a ridge over the northern coast of the Gulf of Mexico.

The NHC anticipated that the system's passage over the Yucatán Peninsula would tighten the wind field and allow for further development in the Bay of Campeche.

[1][8] After moving ashore the Yucatán, Stan traversed the peninsula in about 18 hours, emerging into the Bay of Campeche as a tropical depression on October 3.

[9][10][1] A strong area of high pressure over the western Gulf of Mexico forced the storm to turn southwestward, back to the Mexican coastline.

After the storm moved over the Bay of Campeche, Mexico issued hurricane warnings between Cabo Rojo to Punta El Lagarto on October 3, about 27 hours before landfall.

[1] The NHC had anticipated that landfall would not occur for 48 hours; it later wrote that the agency had "not predicted very well", describing the southwest path as "unexpected".

The armed forces evacuated the inhabitants of a dozen or so towns on the coastal plain, between World Heritage Site Tlacotalpan in the west and the lakeside resort of Catemaco in the east.

[23] Across southeastern Mexico, Hurricane Stan dropped heavy rainfall, resulting in damaging floods that killed 98 people.

The storm produced floods and landslides across eight states in southeastern Mexico, with the most severe effects in Chiapas, Veracruz, Oaxaca, Puebla and Quintana Roo.

Floods and mudslides affected much of Chiapas, with monetary damage costs estimated at Mex$8.8 billion (US$819 million), representing about 5% of the state's Gross Domestic Product (GDP).

Rainfall in the state reached 566 mm (22.3 in) at a station called El Tejar, located near where Stan moved ashore.

[25] As the system progressed inland towards the Sierra Madre del Sur to the west of the Isthmus of Tehuantepec, the states of Oaxaca and Chiapas were affected with torrential rains.

Many communities were overwhelmed, and the worst single incident appears to have occurred in Panabaj, an impoverished Maya village in the highlands near Lake Atitlán in Sololá department.

This volcanic lake was so overwhelmed by the torrential rains that many of the small, Mayan villages covering the shores experienced landslides from above.

The October 1 eruption of the Santa Ana Volcano, located near the capital San Salvador, compounded the problems, which led to even more destructive floods and mudslides from Stan.

According to the director of El Salvador's National Emergency Centre, 300 communities were affected by the floods, with over 54,000 people forced to flee their homes.

[citation needed] A spokesman for the Salvadoran Red Cross said that "the emergency is bigger than the rescue capacity, we have floods everywhere, bridges about to collapse, landslides and dozens of roads blocked by mudslides".

Mexico's Secretariat of Social Development hired 1,804 cooks and set up 270 temporary kitchens to feed people in the aftermath of the storm.