how to calculate significance value of lag correlation?

I have cross correlate the monthly rainfall and groundwater.

     % code 
[XCF, Lags, Bounds] = crosscorr(flipud((gw')), flipud((rainfall')),6,2);

end

The lag values of 6 months are given below

% code
end
-6  -0.19
-5  -0.49
-4  -0.68
-3  -0.68
-2  -0.47
-1  -0.11
0   0.31
1   0.67
2   0.79
3   0.72
4   0.49
5   0.16
6  -0.16
Now I want know that lag values are significant or not. how to calculate the p-value of each lag.

Answer 1

[Alex Backer]

I wrote some code to estimate the p-value empirically:

Alex Backer (2020). xcorrpvalue (https://www.mathworks.com/matlabcentral/fileexchange/75403-xcorrpvalue), MATLAB Central File Exchange.

Hope it helps.