• What can we usually expect during this period?
  • Climatically, September to November forms the second half of the wet season in the Caribbean islands and in Belize. During this period, a large number of wet days and frequent wet spells occur. However, a number of short dry spells still can punctuate this season, particularly in the Greater Antilles.
  • By contrast, the Guianas are in their hot, dry season, running into November in most areas, but continuing through April in far inland, southwestern parts of the region. Hence, frequent dry spells, but infrequent wet days and wet spells are the historical norm from September to November.
  • The 2024 Atlantic Hurricane Season officially lasts until November 30th, with the peak of tropical cyclone activity typically lasting until mid-October, but storms and hurricanes have occurred after the official end date.
  • September and October form the last two months of the Caribbean Heat Season. These months are characterised by higher night- and daytime temperatures, peaking air humidity and a high frequency of heatwaves through September in The Bahamas, Belize, the Greater Antilles and the Leeward Islands, through October in the ABC Islands, Barbados, the Guianas, Trinidad and Tobago and the Windward Islands.
  • In the Caribbean islands and Belize, the ground surface and soils become more moisture-laden, often to the point of saturation. When intense showers occur, the potential for flooding, flash floods and associated hazards and impacts such as land slippage, rock fall and soil erosion is particularly high. With a full foliage, potential wind damage related to tropical cyclones is increased. On the bright side, wildfire potential, the concentration of airborne particulates, the frequency of Saharan dust incursions and local dust levels should be low during this period. Access more detailed forecast information on dust and air quality in the Caribbean here: http://dafc.cimh.edu.bb/.
  • By contrast, with a peaking frequency of dry days and short dry spells, the ground surface and soils in the Guianas usually lead to a reduction in flood potential, but an uptick in wildfire potential, the concentration of airborne particulates and local dust levels.
  • Across the region, swells, surges and rip currents from tropical cyclones – even if remotely located –, can be particularly hazardous to life and engender beach erosion. (Seven-day forecasts of swell heights may be found here: https://marine.cimh.edu.bb/#/model/WaveWatch%203/Regional).
  • Notwithstanding that it is the wettest part of the year in the Caribbean Islands and Belize, there remains a high risk of skin damage due to intense ultraviolet (UV) light emitted by the sun. The UV index will progressively decrease from extremely high (11-12) to very high (9-10) on sunny days towards November.

• What is different this year?
  • Cooling temperatures in the equatorial Pacific may possibly result in a progressive transition to La Niña while (near-) record warm surface temperatures in the Caribbean and Tropical North Atlantic Ocean are set to continue.

• The September-October-November 2024 outlook In further detail:
  • The September to November second half of the Hurricane Season is predicted to be even more active than average, possibly ending up with 15 more named storms, 9 hurricanes, and up to 3 major hurricanes (medium confidence). However, even higher numbers cannot be excluded.
  • Seasonal night-time and day-time temperatures in the Caribbean are expected to be even warmer than usual and accompanied by even higher than usual levels of air humidity (high confidence).
  • Frequent and/or long-lasting heatwaves are expected, especially in September. At least 25 – and possibly up to 50 or more – heatwave days are expected over this three-month period in Barbados, the Guianas, Trinidad & Tobago and the Windward Islands, leading to high heat impact potential in these areas (high confidence).
  • More information on the expected heat and its implications on society and environment can be found in the latest Heat Outlook product issued by the CIMH at: https://rcc.cimh.edu.bb/heat-outlook/. Note: In the aftermath of a debilitating severe weather event, exposure to the combination of humid heat and recurrent heat waves can become severely dangerous to human life if unmitigated.
  • Rainfall totals from September to November are likely to be the usual or higher across the ABC Islands, the Greater Antilles and the Leeward Islands, but, possibly, the usual or less in Barbados, Belize, eastern parts of the Guianas, Trinidad & Tobago, and the Windward Islands (medium confidence).
  • Flash flood and long-term flooding potential arising from intense showers will be extremely high (i.e., occurs at least once in most years) throughout The Bahamas, Belize, the Greater and Lesser Antilles, but also high (i.e., occurs at least once every two years) to extremely high across the remainder of the Caribbean region. Persons should keenly monitor weather advisories issued by the National Meteorological Services and other information provided by the Caribbean Disaster Emergency Management Agency (http://cdema.org/) and the US National Hurricane Center (https://www.nhc.noaa.gov/).
  • In line with the forecasted intense wet season, drought concerns by the end of November in the Caribbean are few, with the exception of Trinidad and French Guiana, where long-term drought is still evolving (medium confidence).

This Bulletin provides a broad overview of climate conditions up to 3 months in advance. It is based on insights drawn from CIMH’s suite of technical climate information products and epidemiological insights from CARPHA and PAHO. The information contained herein is provided with the understanding that the CARPHA, the PAHO and the CIMH make no warranties, either expressed or implied, concerning the accuracy, completeness, reliability or suitability of said information. The Bulletin may be freely used and disseminated by the public with appropriate acknowledgement of its source but shall not be modified in content and then presented as original material.