Working online while on vacation in the US

I'm sure it must have been asked but I can't seem to find answers anywhere, I work for a Canadian company and my job can easily be done online by connecting to the servers from my computer. I'm planning a 2 weeks vacation in the US for next year and I want to know if I'll need a Visa (and which) in case there is an emergency and I have to log in a few hours. Also, should I particularly enjoy my stay, I could also extend it for a month, though I would effectivily be working online full time after my 2 weeks paid vacation.

Less than 90 days stayed, less than 10K earned, if that changes anything. Thanks.

It depends on whether your firm has US connections or not. If they do, you cannot do any work while in US, other than read/respond to e-mails

Bah we have a few US clients. I just want to take a month or 2 off or winter :/