While doing home inspections in and around Charlottetown, I have noticed on many occasions homeowners using extension cords outside or under buildings in a way that is a safety hazard.
First off, extension cords are meant to temporarily plug something in, and not as permanent wiring. If the home needs permanent wiring outdoors, you should have a qualified and licensed electrician run proper wiring with proper weather resistant conduit.
Secondly, if you do use an extension cord outside, make sure you use an extension cord that is rated for outdoor use. Extension cords rated for indoor use may easily wear, leaving wiring exposed or broken. Never use a cord that feels hot or is damaged. Touching even a single exposed strand can give you an electric shock or burn.
Thirdly when using outdoor extension cords, or plugging into any exterior outlets, make sure the outlet is GFCI (ground-fault circuit interrupter) and test before using. GFCI outlets have been required on all exterior outlets on new builds for a while now. Even if you think your outlets are grandfathered in, In my inspection report I always recommend that all exterior outlets be converted to GFCI for your protection and safety.
And finally purchase only extension cords approved by an independent testing laboratory, such as Underwriters Laboratories (UL), ETL-SEMKO (ETL) or Canadian Standards Association (CSA).