Excessive Heat — Mayaguez and Vicinity, Puerto Rico

2023-06-01 to 2023-06-30 · Mayaguez and Vicinity, Puerto Rico

Event narrative

Several Mesonet stations reported heat indices surpassing 108 degrees (local heat advisory criteria), and even 112 degrees (excessive heat warning criteria) for a prolonged period of days, mainly from 10 AM to 4 PM AST. The reports were widespread along the station network.

Wider weather episode

Extremely hot conditions persisted through the entire month of June for all the climatological sites. Several factors contributed to this hot spell. First of all, the wind flow was persistently from the south to southeast bringing typically warm air into the area, and once that air mass crossed the Cordillera Central In Puerto Rico, the air warmed even more when descending. Second, subsidence associated with a near stationary mid-upper level ridge warmed the air mass. The extremely anomalous sea surface temperature possibly increased the moisture content in the environment, causing very high heat indices. The lack of clouds and rain also allowed for more sunshine to reach the surface, so temperatures rose quickly each day. Finally, urban heating exacerbated the very high temperatures in the region. Under these conditions, twenty (20) excessive heat warnings and twenty-seven (27) heat advisories were issued for several parts of Puerto Rico. Several stations across Puerto Rico, including Culebra reported heat indices surpassing 112 degrees, and on the hottest days, up to 120 to 122 degrees. The areas with the highest temperatures were the coastal and urban areas of the north and west, the valleys of the eastern interior, and Culebra.

Source: NOAA Storm Events Database, event_id 1104738. Narrative written by the NWS forecast office that issued the report.