What should scientists consider when studying tree rings to understand the variations in the local climate

The tree rings are not all the same, and they can be a very nice indicator of the climate patters at a certain location. Some rings are small and thin, some rings are big and wider, and this is due to the climate. While some trees are able to grow in 2/3 of the year, or half of the year, some can only grow only in a period of around 3 months, and this will define the appearance of the rings of the trees. The ones that have longer vegetative period will have bigger and wider rings, while the ones that have a short vegetative period will have small and thin rings.