Tempo runs

I'm not really very good at these. Today's schedule called for a mile warm up which i took nice and slow as it was almost 90 degrees and humid... then 2 miles tempo... I don't have a running watch so I have to go on how it feels. I managed about a mile and then slowed back down. I felt like I was struggling. I finished 4 miles total but it was about distance not speed. I'll try again next week.