That would give you the correction to what it's SG would be at 80degrees F. It's not a significant difference.

From Rolls battery, 'for a new, fully charged battery, at an average temperature of 50 degrees F, the battery will self discharge at about 0.0003SG per day. They calc. from a SG of 1.265(fully charged), it will take 250 days to self discharge to a SG of 1.190(freezing point at -12 F)'

That's a dead battery. If you're in a colder climate(like yours or mine), it will take much longer to self discharge to that point, year and a half or so. If I left a new fully charged battery in my boat in Maine for a year, it would have a SG of about 1.275

This is all according to Boat Owners Illustrate Electrical Handbook by Wing. Interesting stuff.