The following chart plots the average performance of the FTSE 100 Index during February since 1984.
As can be seen, historically the market tends to rise for the first two-and-a-half weeks and then drifts lower for the rest of the month.
January 2015
The following chart shows the average performance of the market in January (1984-2014) and overlays the actual performance in January 2015.
The market was unusually strong around the third week of the month, which led to its out-performance of the historic average for the month.