I think the problem is your browser is too old. According to your specs, you're using Firefox on Win7, which means you're probably using Firefox 115 ESR.
I get exactly the same error as in your post #1 if I use Firefox Portable 115.22 ESR. I do not get any error if I use R3dfox Portable 128 ESR or 142. R3dfox is a fork using the same open source base code as Firefox.
My belief is that the ESR versions are kept up-to-date with security updates but do not get the non-security updates. (See
discussion here.) Thus, FF115 ESR gets v142 security updates but non-security updates are frozen at the 115 level. R3dfox 142 gets both security and non-security updates from FF142.
Thus, Firefox 115 may be up-to-date security-wise, but does not include non-security features added in later versions only available on Win 10/11. The weather.com website must be relying on back-end CMS features that are only available in "modern" browsers released after FF 115. Thus, the crashing on a 115 browser.
In contrast, r3dfox uses the same base code being used in later Win10 Firefox versions but is back-porting it to be able to run on Win 7, even though the Firefox devs won't do that themselves. Thus, r3dfox 142 is using the same base code as Firefox 142 but running on Win7. My guess is the weather.com CMS is happy with the 142 code (and apparently even with the FF128 ESR code), so doesn't crash.
The bottom line is Firefox 115 may still be secure (for now) but is just too old. Switch to a
more modern browser.
Note the same issue probably exists in the Chromium camp. Chrome ceased Win7 support with v109, but a number of forks have continued to back-port post-109 non-security updates in their forks for Win7.