  In this study we describe an innovative method to determine potential sites
for optical and infrared astronomical observations in the Andes region of
northern South America. The method computes the Clear sky fraction (CSF) from
Geostationary Observational Environmental Satellite (GOES) data for the years
2008-12 through a comparison with temperatures obtained from long-term records
of weather stations and atmospheric temperature profiles from radiosonde.
Criteria for sky clearance were established for two infrared GOES channels in
order to determine potential sites in the Andes region of northern
South-America. The method was validated using the reported observed hours at
Observatorio Nacional de Llano del Hato in Venezuela. Separate CSF percentages
were computed for dry and rainy seasons for both, photometric and spectroscopic
night qualities. Twelve sites with five year averages of CSF for spectroscopic
nights larger than 30% during the dry seasons were found to be suitable for
astronomical observations. The best site with (220$\pm$42) spectroscopic clear
nights per year is located in the Andes of Venezuela (70$^{\circ}$28'48"W,
9$^{\circ}$5'60"N) at an altitude of 3480 meters. Lower quality regions were
found in Sierra Nevada de Santamarta and Serran\'ia del Perij\'a with
(126$\pm$34) and (111$\pm$27) clear nights per year, respectively. Sites over
the Andes are identified in Norte de Santander with (107$\pm$23) and in the
north-east part of Boyac\'a with a mean of (94$\pm$13) clear nights per year.
Two sites at low latitude located in Ecuador with more than 100 clear nights
per year and with similar seasonal CSF percentages were also identified. Five
year evolution suggest a possible correlation be tween the lowest percentages
observed during the rainy seasons of 2010 and 2011 with positive values of the
Southern Oscillation Index.
