Climate　warming　and　increasing　variability　challenges　the　electricity　supply　in　warm　seasons.　A　good　quantitative　representation　of　the　relationship　between　warm-season　electricity　consumption　and　weather　condition　provides　necessary　information　for　long-term　electricity　planning　and　short-term　electricity　management.　In　this　study,　an　extended　version　of　cooling　degree　days　(ECDD)　is　proposed　for　better　characterisation　of　this　relationship.　The　ECDD　includes　temperature,　residual　temperature　and　specific　humidity　effects.　The　residual　temperature　is　introduced　for　the　first　time　to　reflect　the　building　thermal　inertia　effect　on　electricity　consumption.　The　study　is　based　on　the　electricity　consumption　data　of　four　multiple-street　city　blocks　and　three　office　buildings.　It　is　found　that　the　residual　temperature　effect　is　about　20%　of　the　current-day　temperature　effect　at　the　block　scale,　and　increases　with　a　large　variation　at　the　building　scale.　Investigation　of　this　residual　temperature　effect　provides　insight　to　the　influence　of　building　designs　and　structures　on　electricity　consumption.　The　specific　humidity　effect　appears　to　be　more　important　at　the　building　scale　than　at　the　block　scale.　A　building　with　high　energy　performance　does　not　necessarily　have　low　specific　humidity　dependence.　The　new　ECDD　better　reflects　the　weather　dependence　of　electricity　consumption　than　the　conventional　CDD　method.　©　2017　IOP　Publishing　Ltd.