I want to try to predict the USA summer highs using a linear regression. I know I can probably take data from the last 10 summers and plug that in, and use that to predict, but I'd like to use two data sources. 1 data source from the historical highs from past summers in the USA, and the 2nd data source from the historical highs from past summers from another country like Australia who has opposite seasons from us in the USA. Is it possible to do a linear regression from two data sources, and use both of them to predict a number? Do you think this is a more accurate way of doing this? Or is it just as accurate as using one data source like historical USA highs.