Table III
Approximate salinity, in parts per thousand, for the hydrometer reading at the indicated temperature
Temperature Specific Gravity
Here's the tables which demonstrate this issue. For instance, at 76 degrees and 1.025 SG, you are at 35ppt salinity.
F C 1.020 .021 .022 .023 .024 .025 .026 .027
74.0 23.3 28.0 29.3 30.6 31.9 33.3 34.6 35.9 37.2
75.0 23.9 28.2 29.5 30.8 32.1 33.5 34.8 36.1 37.4
76.0 24.4 28.4 29.7 31.0 32.3 33.7 35.0 36.3 37.6
77.0 25.0 28.6 29.9 31.2 32.5 33.9 35.2 36.5 37.8
78.0 25.6 28.8 30.1 31.4 32.7 34.1 35.4 36.7 38.0
79.0 26.1 29.0 30.3 31.6 32.9 34.3 35.6 36.9 38.2
80.0 26.7 29.2 30.5 31.8 33.2 34.5 35.8 37.1 38.5
81.0 27.2 29.4 30.7 32.0 33.4 34.7 36.0 37.4 38.7
82.0 27.8 29.6 30.9 32.3 33.6 34.9 36.3 37.6 38.9
83.0 28.3 29.8 31.2 32.5 33.8 35.2 36.5 37.8 39.2
84.0 28.9 30.1 31.4 32.7 34.1 35.4 36.7 38.1 39.4
85.0 29.4 30.3 31.6 33.0 34.3 35.6 36.9 38.3 39.6
86.0 30.0 30.5 31.8 33.2 34.5 35.8 37.2 38.5 39.8
87.0 30.6 30.8 32.1 33.4 34.8 36.1 37.4 38.8 40.1
However, this is the easy way to do it. Even most elcheapo hydrometers adjust for temperature automatically.