Maybe rain slows my internet connection

Last week, I realized that it seems to be every time it rains, my internet connection slows drastically.

This last rain is an example. The Ookla speed test showed: 2.28 Mbps down and 21.40 up. So in the rain, I was getting 2.28 instead of the 600 Mbps that my plan is supposed to give me.

The days before the rain, I was getting 703.35 Mbps and similar. So, that exceeds the plan.

After the rain stopped, the speed went up to 93.67 a 5:30 AM. Then later that morning, at 10:00 AM, I got 329.34 Mbps. Maybe something is drying out?

The following day at 5:30 AM, I got 525.38 Mbps which is short of what the plan is supposed to give me, but I suppose it is close enough.

Finally, at 6:00 AM, the next day, I got 661.75, delivering a little more than the plan. 

Now, the speed is between 250 Mbps and 385 Mbps. It did not notice rain so much. So, I am not sure what it is. But I am sure that the speed tests have shown speeds far lower than what my plan is supposed to give several times recently.

The computer I run the speed test connects directly to my Netgear Nighthawk router. There is no Wi-Fi issue because it is hard-wire connected. In addition, the router is indoors on a shelf, so there is no water issue with the router.

I have restarted my modem hundreds of times per the "support" and the automated chat. I don't see that restarting my modem affects the speed. After restarting, sometimes the speed is faster and sometimes even slower.

Is there any way in the Xfinity that I can get a live person to look at the speed issue when it arises?