Hey you can see visibility and temperature has a positive correlation of 0.39 which is good but not so much, in the graph too you can see a positive trend the graph is tilting toward the top right side(a little). It seems like with increase in temperature visibility is increasing(most times), but that is not the case always. Try to imagine and draw a line through the graph, you will be able to see a Straight line though the points are dispersed a little.
About the second question, yes Linear Regression can be applied to this data but I am not sure if it is the best algorithm that can be applied try applying other models too and see which one works best.

Yes,
I watched the second lecture yesterday. I will try to apply logistic regression on this dataset and try to determine rain or snow because that seems like a proper problem for this dataset