@jtappin play with the White Balance Temperature and Tint sliders in RawTherapee until the preview looks right, then copy and paste this setting to all other photos taken in the same light. If any photos captured a neutral-colored object, e.g. a not-clipped white piece of paper or white shirt or white car, you could take a white balance sample off of them. But in the end just choose something which looks good.
You could also take a sample from the dark part of a cloud if it's daylight and the sun is not low in the sky, it often looks good. In this example I sampled the area marked with the L*a*b* color picker: