Seasonal Forecast: May to July 2021

Seasonal Forecast: May to July 2021

Date of Issue: May 9th, 2021


Ø Seasonal Forecast: May – June- July 2021 (MJJ)



The onset of the wet season may be delayed by up to one month across the Lesser Antilles, including Dominica. A decrease in the frequency of wet days (wet day: greater than or equal to 1.0mm of rainfall) is expected with a slight reduction in extreme wet spells. Therefore, conditions across the area may be drier than usual by the end of July.  This may lead to extended dry spells which can result in significant water stresses within the agricultural sector, particularly along the western half of the island. A need for irrigation and other water harvesting techniques may be required. In spite of this, any wet spell event in the period has a moderate to high chance of producing flooding and its associated hazards. Keep updated.



May marks the start of the Heat Season and temperatures generally begin to increase. For the MJJ period, both night-time minimum and daytime maximum temperatures are likely to be usual. Heat stress may appear and would peak during heat waves.


Ø Influencing Factors

1.      El Niño Southern Oscillation (ENSO)


Recent observations: Neutral ENSO to marginal La Niña exists as Sea Surface Temperatures (SSTs) in the eastern Pacific have warmed slightly.


Model forecast and guidance: Models favor ENSO neutral conditions throughout May to July (80% confidence). However, large uncertainties exist as to whether this will persist through the second half of the wet season or whether La Niña conditions will return. If La Niña re-emerges, the region can expect to be at least as wet or even wetter than usual, with the potential for a busy peak of the Atlantic Hurricane Season.


Expected impacts on rainfall and temperatures: Transitioning out of La Niña tilts the odds to somewhat drier conditions during MJJ. This may also lead to a delayed onset of the wet season. The severity of heat impacts is usually reduced during the Heat Season, post a La Niña event.   


  1. Climate conditions in the Tropical North Atlantic (TNA) and Caribbean Sea


Recent observations: SSTs have cooled close to average in the Caribbean and the Tropical North Atlantic (TNA) and remains about 0.5°C above average in the Sub-tropical North Atlantic.

Expected conditions: Uncertainties exist in the forecast of the SSTs across the Caribbean Sea and the TNA through June-July-August 2021.

Expected impacts: Though SSTs have cooled slightly in and around the Caribbean, they remain warm and could contribute to above-average humidity, seasonal rainfall totals, reduced dry spell frequency and a potential slightly earlier start of the wet season in the Lesser Antilles.



See table below with Climatological Normal/ Averages



Accumulated Rainfall (30 years)


Canefield Airport

Douglas-Charles Airport


370.2 to 630.7mm

470.2 to 765.1mm

Wet days Normal

Forecast (MJJ 2021)

35 to 59

29 to 51

45 to 66

37 to 59

7- Day Wet Spell Normal

Forecast (MJJ 2021)

2 to 5

2 to 6

2 to 5

2 to 5

7 day dry spell


0 to 2

Temperature (15 years)

Average Maximum

31.4 to 32.2°C

30.2 to 30.7°C


27.8 to 28.3 °C

27.4 to 27.8°C

Average Minimum

24.0 to 24.6°C

24.6 to 24.9°C