@ziya89
When I start Opera, it opens a couple of dozen processes (all named "Opera"). Plus an Opera Update process. Depending on how much maintenance and updating Opera requires, a lot of CPU threads might be worked pretty hard for a few minutes.
Recommend go to the website of the manufacturer that made your CPU. Find out what the maximum allowable Temperature is. Temperature rising might not be a problem if it's not going above the max allowed temperature.
Laptops and desktops are designed to provide sufficient cooling even if all the cores are working a sustained 100%. If your CPU is going over the max allowed temperature, then the heat-sink compound on the CPU might need refreshing. Or if it's a laptop, its air-ducts might need cleaning out.
Hopefully, your laptop has a hatch over the air duct and CPU that you can open, and remove any dust bunnies. It doesn't have to be a perfectly clean job, just a periodic one. Can of compressed air is optional. Worse case is if the laptop has no hatch, but instead needs to be disassembled to access the air duct and CPU. In that case, maybe youtube has a video showing how to [partially] disassemble Your particular laptop so you can access the air duct and CPU. And then you gotta decide if it's something you can do or if the laptop will need professional help.
My laptop is old, they hadn't invented hatches yet, so it requires partial disassembling to clean out the duct, which I've never had done. Instead, I turn off the laptop, fold it up, and puff hard a few times into the exhaust vent. That usually results in a big puff of dust jettisoning out of the air intake. To be concise, I'm blowing into the duct with a puff of air that's going opposite of the air's normal direction, which pushes accumulated dust away from the fan and hopefully out the air intake vent. I puff so hard I can hear the fan spinning for a moment. Sometimes I see a puff of dust come out of the air intake, sometimes I don't, but regardless, the CPU's operating temperature drops from the high 60s to the mid 50s, anyway. At high loads, the highest temperature gets into the low 70s before puffing, but stays in the 60s after puffing. The specified high-temperature is 100 degrees C, but it's an old laptop, so I'm not going to wait for the temperature to get close to maximum before refreshing the air duct. When I start seeing 70s, it's high time to blow out the laptop. Besides stressing the CPU, high temperatures would also stress the fan because it has to run faster.
There's probably still some cat hair in there that won't come out just from blowing. But the improvement is probably 99% of what it would be if the laptop were taken apart.
I blow out the laptop in the shower, or outdoors (upwind), because you don't need to let go a puff of accumulated dust in your living area. Recommend: Before you PUFF into the air exhaust vent, point the air intake vent away from you; lol.
For desktops, I take the computer outside and blow out all the dust I can find, especially around the CPU, using a can of compressed air. It doesn't have to be a perfectly clean job, but only periodic. Be gentle so the jet of air doesn't dislodge delicate components.
It's good that you keep an eye on your CPU temperature. I use CoreTemp to keep the temperature displayed continuously in the Windows' toolbar. You can display the temperature of every core (which can take a lot of real estate, with CPUs having so many cores these days). I find it sufficient to set CoreTemp to display the temperature of only the one core with the highest temperature.