It is clear that on the average, the Arctic ice cap is melting away, although the rate at which it is melting varies depending on which month you measure. The ice is diminishing faster in the summer than the winter, although there is a lag between ice extrema and solar insolation. The sunlight is most concentrated late in June and least concentrated in late December (the solstices) but it takes time for the ice to form and melt, a sort of thermal inertia, if you like. The extrema for ice cover are around the equinoxes.

On a month by month basis, the loss/decade of sea ice extent (compared to 1981-2010 average) is:

Sep -12.8%
Aug -10.4%
Oct - 9.5%
Jul - 7.2%
Nov - 5.0%
Jun - 4.1%
Dec - 3.7%
Jan - 3.2%
Feb - 3.0%
Mar - 2.7%
Apr - 2.6%
May - 2.6%

You will note the relative loss over the years varies from -12.8% in Sep to -2.6% in Apr and May,
but it is ALWAYS a loss, regardless of which month we choose to average. Of course, from year to year, the value is noisy (it bounces around a lot due to local conditions or weather), but the general trend over time is ALWAYS down. No matter when you look, what year or what season, the Arctic is melting away. Its just more noticeable in summer.

Sea ice extent in the Arctic is a very sensitive indicator, a barometer, of global warming. And that sensitivity is magnified in summer.