Runners of /r/houston, how much has your pace slowed down in this high heat?

This whole summer, my pace has slowed down about 1-2 minutes per mile versus when I was running in March or April. I've tried switching between waking up early in the morning and running later in the evening but no matter what time of day, the humidity along with the heat makes it suddenly so much harder and discouraging. I'm trying to train for a half marathon that's within the next few months but right now, 4 miles out here feels more exhausting then 7 miles at a faster pace a few months ago!