Isla Juan Fernandez Monthly Temperatures

This post refers to my analysis of recorded monthly mean temperature trends at Isla Juan Fernandez, an island in the southeastern Pacific Ocean.  The station was established in 1901.  The analysis used raw data (as recorded, without any adjustments) as published by KNMI (the Dutch Meteorological Institute).   Polynomial curves of best fit were added to the plots.


The Isla Juan Fernandez station is located in the Juan Fernandez islands, in the Pacific Ocean 670 km off the coast of Chile.  It is probable that the station is located in the small town of San Juan Bautista on Robinson Crusoe Island.

Over the 1901-2016 period (a period of 116 years) the years are 89% complete.

Isla Juan Fernandez has a mild climate.   Mean monthly temperatures vary from 12.3 degC (in August) to 18.8 degC (in February).  Extreme monthly mean temperatures recorded are 10.7 degC (in August 1934) to 21.2 degC (in February 1952).


Mean, Maximum and Minimum Monthly Temperatures


Plots are shown below for annual mean temperature and the monthly mean temperature for each of the 12 months.  A polynomial trendline was fitted to each graph.  A comparison of the monthy trendlines are also presented.   It should be noted that the trendlines (in red) can sometimes be misleading at either end of the series as the line is very dependent on the temperature values in individual years (this sensitivity does not occur away from the start and end of the series).


Annual Mean Temperatures


Monthly Mean Temperature Trendlines



























  • The plots show slight cyclical monthly trendlines in most months, with generally a regular decrease in temperatures over the past century.
  • The average annual temperature trend since 1901 is about -0.3 degC/century.
  • There are no alarming increases in the temperature trendlines in recent decades.


Isla Juan Fernandez is one of  257 stations, worldwide, for which I have analysed long-term temperature trends.   The analyses at 50 representative stations are summarised in the blog post:   world-50-temperatures



Please let me know what you think of my analyses.


The Author:

This article was written by Brian Gunter of Narooma, NSW, Australia. In his previous life Brian was an engineering hydrologist involved over many years in the analysis of rainfall and river flow data for the planning of water resources projects in Australia, Asia and Africa. In recent years he has been one of the Marine Rescue NSW (previously Royal Volunteer Coastal Patrol) volunteer weather observers who operate the Narooma station for the Australian Bureau of Meteorology.




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