does temperature affect speaker performance?

I think temperature has a greater effect on the speed of sound than on the speaker driver's mechanics. This can throw your system off if the speakers were carefully positioned and the room reflections/nodes treated and optimized at different ambient conditions. Sound travel is faster in warmer air temperatures - probably explains what Bryhifi experienced.

Here's an interesting site that can provide a lot of insights with regard to venue acoustics and temperature/sonic speed: (http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe.html) Of course the lower humidity in the winter time will affect sound propagation as well. The expanse of Mylar that makes up the Maggie's main diaphragm, and narrower(but still long) Quasi-Ribbon driver would certainly be subject to expansion and contraction with changes in temp also. My Maggies are in a climate controlled environment, so I don't notice any seasonal difference in sound.

It seems my 1.7 sounds "blown".  I have them in my basement where it sometimes gets pretty cool.  Could this have caused this?

Let me first state that I have little to no scientific experience. But hold on now. Sound travels at 343 meters/ second at 20 degrees C, or 68 degrees F. I would guess that an average listening distance between speakers and listeners ears is close to 3 meters. At that distance the sound from the speaker would reach your ears in less than 1/100 of a second. It seems to this science layman that a few degrees of ambient temperature variance would not render any speed of sound difference detectable by the human ear.There may be other variables involved that Audiogon's mandarins of science can enlighten us about but I tend to agree with the post of pbb, "Maybe your ears are affected by the weather."

Weather affects the power grid, so indirectly affects the speakers. High pressure systems are generally good for the sound, nice sunny ☀️ days, whereas low pressure systems, rainy, stormy days, are generally bad for the sound. Low humidity is generally bad for the sound, what with the static electric charge on everything. I suspect high solar activity is not good for the sound. If that concerns you the daily solar activity is tracked by National Weather Service. Since the acoustic waves all travel at the same speed at a given temperature, the sound should not be affected by changing the overall temperature in the room. However sound can be affected by making a change to temperature in part of the room. A cool trick is placing bowls of ice water on the floor out in front of the speakers. See what that does to the sound. 🤗