I've not experienced it myself, but it may be that your router is overheating due to the high ambient temperatures. If possible try relocating it to a cooler area or find a way to get more airflow over it. e.g. put a desk fan pointing at the router for a few hours to see if it makes a difference.
Also try having your router admin page open for a while. When the internet connection drops out, check to see if you PC is still connected to the router (i.e. find out where the drop out is ocurring - PC to router or router to internet). I don;t know what router you have, but there may also be diagnostic tools on it to look at.