salinity

[Johnny Reefer]

Yes, temperature is a factor on your SG readings.
If you are using a basic hydrometer there is a conversion to apply.
I looked online for a conversion table but could not find anything, within my patience tolerance.
If you can gain access to the book "Natural Reef Aquariums" by John H. Tullock (Revised Ed. January 2001), there is a hydrometer readings conversion table, as it relates to temperature, on page 121.

I suppose the refractometer is doing this conversion for you, but then can the refractometer detect the temperature of only a few drops of water?

At any rate, try to get your hands on, and check out, that book.

Cheers,