A comparison of the ring widths of various Swedish trees with temperature is found to show positive correlations with coefficients at about 0.3. The yearly precipitation in Sweden seems to be sufficient for the growth of the trees, and a comparison of ring widths and precipitation shows nearly zero values of the correlation coefficient. The solar activity and temperature have been compared with observable relations. Finally, a comparison of the tree rings with solar activity shows that broad rings in general correspond to large sunspot numbers, but, at least apparently, the opposite effect has also been recorded—a warning against drawing too rapid conclusions.