Blocked sign-in attempt to Google Account
This question was asked a while ago, I'm not sure if you've solved the problem. If you have, please enlighten me! I've been having the same issue (not quite every time, but almost every time I turn my Mac on). As with you, the location is my hometown.

I've done some Googling, somewhat ironically, and it seems to be a security issue with OSX Yosemite causing it, though I must confess I don't know the details.

This thread says: 


  "I received the same emails the same day I upgraded to OS X Yosemite
  and setup my Gmail account in Apple Mail. Its not a bug, but only
  security changes that have happened on Google's end of things. All you
  have to do is follow the link and enable "Access for less secure
  apps". Thats what I did and I haven't received the emails since."


However, I'm not a fan of allowing less secure apps, in case there is a genuine security issue (which this doesn't appear to be). 

Another discussion says:


  "I've found a way to solve it: just went to Settings, Internet
  Accounts and deleted my Gmail account. Put it back and it's working
  fine now."


It appears to be a fairly common problem (Google "Yosemite gmail sign in blocked"). I have tried the solution above and haven't received any more emails, but if it doesn't seem to work, I'll update this answer.



UPDATE: It happened again, which I'm fairly unchuffed with. After rooting around on Google, I found this:


  Google may block sign in attempts from some apps or devices that do
  not use modern security standards. Since these apps and devices are
  easier to break into, blocking them helps keep your account safer.
  Some examples of apps that do not support the latest security
  standards include:
  
  
  The Mail app on your iPhone or iPad with iOS 6 or below
  The Mail app on your Windows phone preceding the 8.1 release 
  Some Desktop mail clients like Microsoft Outlook and Mozilla Thunderbird 
  
  
  To help keep your account secure, we may block these less secure apps
  from accessing your account, and you’ll see a “Password incorrect”
  error when trying to sign in. If this is the case, you have two
  options:
  
  Upgrade to a more secure app that uses the most up to date security
  measures. All Google products, like Gmail, use the latest security
  measures. Go to Allow less secure apps and choose “Allow” to let less
  secure apps access your Google account. We don't recommend this option
  because it may make it easier for someone to gain access to your
  account.


So, bearing this in mind, it seems to be using a client of some kind causing the issue, which fits in with previous suspicions. So, for anyone facing this issue, be aware that your mail client may not be using the "modern security standards" that Google wants, and that this may the root of the issue. The fix is likely to be wait for an update to the client, or use a different one when accessing your Gmail account (or select "Allow less secure apps" in your Google settings).