CENTRAL AMERICAN RAINFALL. 
19 
6. Variations of Rainfall .—The periodic variations have 
already been noted. The values for different years may 
vary as 2 to 1 or even as 3 to 1 (see columns 5 and 8, Table 
III, p. 24.) The monthly variations are still greater, and are 
greatest for the months following the dry season, especially 
May. This means only that the invierno begins earlier some 
years than others, and the date of its commencement may 
vary a full month. 
Of yet greater interest are the maximum daily rainfalls 
(see column 7, Table III, p. 24), and these are most significant 
when given as percentages of the total annual rainfall. 
Maximum Daily Rainfall. 
Station. 
Month. 
Inches. 
Percentage 
of annual 
rainfall. 
Guatemala. . 
August. 
3.88 
7.2 
Alta Verapaz (Setal). 
November... 
9.58 (212) 
3.39 
4.5 
Salamd... 
June. 
12.1 
San Salvador. 
October. 
2.38 
3.3 
Rivas... 
October. 
4.58 
7.0 
San Jos6... 
July. 
5.04 
7.4 
Tres Rios. 
October. 
3.43 
5.7 
Colon. 
May. 
5.17 
4.2 
Gamboa. . 
August. 
6.23 
6.6 
Panama. 
August. 
6.42 
13.1 
Of the 9.58 inches at Setal, 7.12 inches fell during the 
night. 
The absolute maxima of rainfall can be obtained only 
from long series of observations, and these series are gener¬ 
ally short. It is therefore safe to say that from 7 to 10 per 
cent of the total annual rainfall may descend in one day in 
Central America, and that for the drier invierno region this 
percentage may reach from 10 to 15 per cent. 
This sounds extraordinary, and certainly the fall of from 
4 to 10 inches of rainfall in one day, and usually in a few 
hours, gives one a striking idea of how the rain descends in 
