For me it adds a frisson of excitement to be trying to get a run in before the Sun has properly got his hat on.
The omens were not good. The weather applet in my PC toolbar just said Heatwave! and my browser showed me an advert telling me I was eligible for a free bus pass (still a year to go before I can get one, thank you very much).
In deference to the warmth - it was 25 degrees @ 6:20 am - I walked both times I needed to cross the main road, and did a 33 minute run instead of yesterday's 36. Usually my route is busy with runners but there was hardly anyone out today. Did see an Indian gentleman running shirtless; not sure that's a good idea - I have read that the sun can heat up your skin and it's best to cover up.
I was running with a heart rate target of 135 bpm, which seemed to me a good way to counter a higher temperature; if I'm getting too hot my heart rate will go up, the watch will shout at me, and I'll know to slow down.
In the event all quite comfy, slightly slower pace than yesterday - 5.4 km @ 6:08 min/km, and average HR of 134, so HR within the target. And it's a lovely bright sunny morning!