I had a really great 10 mile run this morning -- better than on Saturday! My wakeup HR was 52, I felt great and completed the run in 2 hours 9 minutes, compared to 2 hours 17 minutes on Saturday. I didn't try to go faster, that was just my "comfortable" pace. That pace extrapolated for 13.1 miles would be 2 hours 49 minutes to complete a half marathon. I hope to run a half in August, and by then I will have been running a weekly 15 mile long-run for about 4 months. My other runs will be two 10 milers and probably one 5 miler as a rest run (right now, the rest "run" is a day of rest, i.e. I'm running three days a week. Starting with July I'll add a fourth day and later a fifth day as rest runs. I should be comfortable with the 13.1 miles, and my "comfortable" pace should be faster than it is now. I hope to complete the half in 2 hours 15 minutes or so.
The temperature was in the mid 30s, but the sky was sunny, and it was a nice day for running!