Run-time efficiency: Cleaning wave date by removing values above calculated threshold

I would like to reduce the run-time of the attached code, all the files needed to make the code run are in the zip attached. This code currently takes 7.6 minutes to run.

    load('SortedHS2009.mat')  
    tic
    for i = 1:length(IndexOfStationsAraeaW)
        stationid=genvarname(num2str(IndexOfStationsAraeaW(i)));
    for imonth=1:12 %Jan to Dec
    index=find(month(Date.(stationid))==imonth); %Find index for current month
    [ToClean]=CleanDataV3(HS.(stationid),index); %Find index of values to set to NaN
    HS.(stationid)(ToClean)=NaN; %Set them to NaN
    end
    end
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