Viewed in terms of the last 10 years, $1.70 is still a decent rate but looked at over the last 2/3 years it is more or less at its lowest point. I trade curencies as a (sometimes profitable!) hobby and haven't observed any particular pattern throughout the calender. The $ lows in 2003 and 2004 came in August/September whereas this year it's late December.
The only thing that is certain is that you can never be certain!!
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