Anything over 78F is hot to me - even 75 can be hot if the humidity is high, like over 85%. In 2006, the temp was 49C during the silhouette BP ctg. match at Hefley Creek Rendezvous (Rendezvous BC 2006). 40C is 122F - the guys were laying or sitting in the grass, out in the sun with rifles over cross-sticks. Before firing a shot, the barrels were too hot to grab with a hand. The shooting was very poor.
Thankfully, the weather change patterns of today have rendered THOSE extremely hot days a distant memory. I know this isn't so for other areas. Stay as cool as you can! Heat can indeed kill.