The relationship is not intuitively clear to me, would like an answer with references and/or graphs. The question arose while reading about Space Shuttle's SRBs.
Increasing Propellant Mean Bulk Temperature (PMBT) increases the burn rate which increases the thrust and causes the motor to burn out sooner. The opposite is true for decreasing PMBT.
This graph from Sutton, 4th edition, shows the effect for large changes in PMBT.
I don't have numbers for Isp but I doubt it affects it much, because both thrust and mass flowrate move in the same direction.
The space shuttle's solid rocket boosters were definitely subject to this effect. The motor contractor Thiokol regularly produced predictions of what the PMBT would be at liftoff, for use in preflight simulations and trajectory design.
I found a few examples in my notes for shuttle mission STS-114
- March 6 / 63 deg F
- May 4 / 69 deg F
- Jul 18 / 83 deg F
Sample Trajectory Design Data Package change notice