0
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Just plot them parametrically [see note}, that is, given for time t and for temperatures T; {t0,T0},{t1,T1},...,{tn,Tn} and snowboard sales S; {t0,S0},{t1,S1},{t2,S2},...,{tn,Sn}, plot temperature against snowboard sales {T0,S0},{T1,S1},{T2,S2},...,{Tn,Sn}.
There is more to this question, as well...