I have a Pixel 8 Pro on Fi. Because it’s relevant later, I live about 750 km east of Los Angeles. When I use the Fi VPN, I notice two oddities.
First, the location services for ads consistently think I’m in Southern California. This isn’t so bad. I wasn’t going to buy a new car or major appliance any time soon, so the fact that the ads I see are for places too far away doesn’t really matter.
Second, and more importantly, the weather widget on the Pixel launcher is wrong, 100% of the time. Last night, it said tomorrow would be sunny with high of 18°C and a low of 8°. When I click it and get into the real weather app, it’s going to 10°/-3°. When SoCal was experiencing record rain, I got a “Coastal Flooding Alert”. I live in the mountains at more than 2km altitude. I needed to see the winter weather warning, because we got three feet of snow last week.
Have I inadvertently turned off a feature that lets Google know where I am when the VPN is on? Turning it off solves 100% of the problems.
That’s sorta part of how a VPN works.
Using a VPN you’re literally moving your location to some other access point on the internet. Use this or a similar site to see where you’re physically attaching when the VPN is on vs off.
https://www.iplocation.net/
I’ve been noticing the same thing (without VPN enabled). I’ve noticed it when my phone (Pixel 6p) is on our home wifi (Centurylink fiber), which is its typical state. VPN is not on. Cell coverage is good.
On the lock screen or home screen I’ve been seeing freezing temperatures and snowflakes for the forecast. What!?! Click to open the full google weather app, and the forecast suddenly becomes location-appropriate (Seattle: more rain…). Back on the home screen the temperature and weather icon will now be correct… at least until next time it happens.
IP geolocation for my external IP4 address right now says Tukwila, WA. IPv6 is through HE tunnelbroker, and geolocation for that reports Seattle, WA. (Neither of those locations have seen snow during the period in question.)
I don’t use the VPN, and on my Pixel 7 it’s been completely wrong about the weather for the last couple weeks. What’s strange is it has my location correct, but I know it wasn’t 75 degrees when we were in the middle of a BIG snowstorm.
I’m laughing now because I just got the P8 Pro on Fi and just yesterday noticed the issue with the weather widget. It has been driving me crazy. I’m glad someone else has noticed it.
The Google VPN will move the device’s IP address to Mountain View, CA, which is Google’s HQ.
The phone will still say that you’re in “X” location if the GPS is on.
You might have on the setting where your device will use your wifi to determine its device location without GPS and, therefore, is"fighting" with your VPN.
Look for “WiFi Scaning” in the location services and turn it on/off and check to see if there’s a difference.
YUP!
Started a couple of weeks ago and has been wrong ever since. Super aggravating because if you tap it the webpage it takes you too is right, and for the next hour or so your At a Glance weather will be right. I’ve double checked Weather’s location access is set to precise, I tried turning access off and on, and multiple phone reboots. None of the other weather apps I use have this problem, just Google, with a Google VPN, on a Google Network with a Google phone.
Honestly I think Google is getting ready to kill Fi and this is just a symptom.
Did the US switch to the metric system without me knowing it?
I should have added that I understand how VPNs work. The Fi VPN, for example, is a split tunnel, meaning that it intercepts traffic destined for outside your local network but lets traffic for your home wifi through uninterrupted so you can access your printer and your smart home devices.
There are multiple sources of location data, and I’m surprised that the Pixel launcher’s At a Glance widget is using IP-based locations when Google One includes the VPN. I turned off the VPN, and now I get accurate At a Glance weather. 
Yes I have this issue. The weather widget shows the wrong forecast until I click it and open it and then it suddenly realizes my true location.
VPN moves your data connection location, but your phone uses other sensors to determine its location. I use the Fi VPN and your link shows me at Mountain View, CA. That’s on the opposite side of country from me. Yet my weather location is always correct no matter where I am. The same for emergency notices and other services like Door Dash, etc. I’m guessing that OP has some problems with location services other than the data connection that are impacting this.
A VPN literally spoofs your location. It does this as a security measure to further hide your virtual identity, ALL good VPNs do this.
I use the metric system at work for science, so it makes sense to me.
You can always change the settings to reflect in Celsius
Can confirm similar results… I used to keep my Pixel 6a on LTE, or else whilst at work, my phone would constantly hunt for 5G and run the battery down. Weather location results were consistent and accurate on LTE. Recently, they re-configured the cell repeaters at work, so I figured I’d give 5G a try again… I’m in the northeast and take my phone out of my pocket to find the weather info on my lock screen says it’s sunny and 75. Not sure where it thinks I am, but weather info has gone to hell on 5G.
I am very aware of how VPNs work. It doesn’t spoof your location, it routes your data through another IP address which has a different geocode, which is different than spoofing. Spoofing implies that you are faking credentials to pretend to be someone else.
The problem is that the Google Weather app shouldn’t be grabbing location from a shitty geocode of an IP address when it has access to my GPS lat/long location. The Accuweather app and MyRadar don’t seem to get confused when I have the VPN turned on, why can’t Google figure it out?
