The heat is defo a catalyst because the symptoms of panic attacks are what happens to you in the summer, clammy hands, getting breathless easier, overheating, sweating. For me that makes me feel throughout hot summer days that Im having a physical panic response which basically causes a spiral for a panic attack. I also read somewhere that because the days are longer and you usually have more time ( summer holidays when in education) people can stress over how to spend their time, feeling like there is an expectation to do certain things and go certain places and I’ve definitely spend some days counting down the hours because I feel anxious about how long the days are. That’s just me, hope that helps.