Nexus Wireless Charger Doesn't Stick in the Heat

I grabbed a wireless charger from Google the day it came out for the Nexus 4. After a few weeks, I noticed a little issue where the phone would slide off. After wiping it down, the problem seemed to go away.

But this week, with the heat wave, the issue is back in full force as the heat seems to partially melt the sticky plastic and the phone just slides right off.

Is anyone else having this issue?