Is it normal the USB flash drive or microSDXC drive plugged into a Macbook Pro is very hot?

I have a 2014 Macbook Pro, and sometimes I plug in a USB Flash drive (the tiny ones) or microSDXC flash drive (microSDXC together with a USB adapter).

But even if I don't use the drive at all, just letting it idle, when it is plugged in for an hour or two, I touched it, and it could be 40-45°C (104-113°F).

If it is actively used, like if I copy files onto it once in a while for an hour, it could be up to 60-70°C (140-158°F). Is that normal? It is high temperature enough to cook an egg. Is the USB output from the Macbook Pro stronger than usual that make the USB drive hot?

(To make sure I don't have fake products I even ordered the USB flash drive and the microSDXC and USB adapter directly from SanDisk, so they should be authentic.)

P.S. I also tried and used a microSD adapter and used it on the Macbook Pro, and it was much cooler, so certainly we can use the microSD port, but what if a user wants to use the microSD port and the USB port at the same time for more storage? What if the user want a low profile USB flash drive as storage?

This is not an Apple issue because it’s the USB device itself (the microSD card) that’s getting hot, not the MacBook.

A device gets hot because electrons are flowing across the conductive surfaces causing friction. Those electrons are flowing because it’s in use.

Why does the USB-C Ethernet adapter get hot, even when unplugged from ethernet?

“In use” doesn’t mean when you are copying files to/from it. As long as it is being recognized by the system, it’s in use. To be candid, I am surprised to see temperature readings with such specifically and only a ~10% variance at idle and an even tighter variance at higher temperatures all measured by “touch.”

Is the USB output from the Macbook Pro stronger than usual that make the USB drive hot?

Unless the power is negotiated using the new Power Delivery specification, which it isn’t because an SD card is not a “power” device to be recharged like an iPhone, its receiving 5V at the current “requested9 (probably 100mA or less) because it’s attached to the USB bus.

One thing to remember is that a source (MacBook, charger, power supply, etc.) doesn’t push power. The device draws power.

Finally, just grabbing a random specification sheet (Transcend) for a SDXC card, the operating environment is -25C to 85C (-13F to 185F) , so you are well within its temperature ranges.