If it is Wireless may be the water molecules get into the signal and space out the info slowing down the stream (J/K

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Run a trace and see where the slow down occurs.
Download this trace program,
http://www.d3tr.de/download.html
Use the Trace as List feature
Output should look like this,
http://www.ezlan.net/network/trace.jpg
The table shows the result of multi ping from my computer through a Buffalo Router to Internet site 96.6.68.195*
The important columns in the table (for this discussion) are the two in the middle. I.e. Min. ms and Max ms.
The numbers there show a typical outcome. As the trace progress on the Internet the variation changes dramatically.
So while the variation on my Router is 1ms, and the connection to the direct ISP's server is 2ms, the variation later on is almost 20ms.
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* The target IP number is an Akami server. Akami servers are probably the best server system on the Internet far surpass most the gaming servers.