What do you want the picture to look like at the rain gauge stations? Do you just want to plot, say, a red circle at the (x,y) coordinates of the stations? If so...
plot(x, y, 'ro', 'MarkerSize', 15, 'LineWidth', 2);
If you want something fancier, like a small image, then you'll have to paste it over the image with indexing or masking.