I tried to do day 3 of the 'couch to 5k' today and it was 25 ish degrees at 9.30 this morning - I just couldn't do it, there was no shade and I had to stop

I'm so pissed off, it's going to have to be Monday that I go again as it's just as hot tomorrow apparently.
I started this week (at least 4 stone overweight, 40 yrs old and never having run for 25 years) and I just want to GET ON with it.