In the traditional culture of our country, relative to the behavior of the climate, the heatwave is considered a hot and dry season in the middle of the rainy season. The Tico peasant waits for her between July 15 and August 15.
Meteorologically speaking, the "canícula" is a longer event than the summer of San Juan; It occurs between the months of July and August, more specifically between July 1 and August 17.
The heatwave is manifested as a decrease in the quantity and intensity, or, a total suspension of the rains that can last from 5 days to 15 days; where, in addition, an increase in temperatures and trade winds is perceived. The heatwave is generally seen in the North Pacific, Central Valley, Los Santos Zone and the General Valley.
Until now, the intensification of the trade wind due to variations in the position and intensity of the high pressure system located in the North Atlantic Ocean has been accepted as the origin of the heatwave. However, other factors such as the El Niño / La Niña phenomenon, the Sahara dust thrusts and the Madden-Julian Oscillation (MJO) can also modulate their occurrence and intensity (measured by the number of dry days, consecutive and not -in a row).
Annual cycle of rain in Liberia (Guanacaste). The heatwave is denoted by the decrease in July and August in relation to the other months of the rainy season. Source: IMN
In the particular case of 2021, El Niño or La Niña is not forecast for July or August, therefore, the heatwave will not be influenced by these phenomena. Agree
With the forecast of global and regional dynamic models, the heatwave will be perceived normally in the second half of July and the first half of August, and would affect the North Pacific and the Central Valley (does not include the Nicoya peninsula, Zona Los Santos and the General Valley).
It is important to reiterate that, although it is probable that the canicules appear on those days, they would manifest themselves in a similar way to the transition period: with a sequence of consecutive dry days followed by some rainy days, then again several dry days and so on. throughout the second half of July and the first half of August.