It is hard even to imagine a day without the sun. If the sun doesn't come out for a day vast changes will have to be made.
Firstly the lights will be kept on even during day, as without the sun darkness would prevail over us. Also without the sun, our earth wouldn't get heated, and the day will be a chilling cold one, so heaters have to be used too.
Next the plants won't be able to carry out photosynthesis in absence of the sun. Although for a single it won't hurt if no oxygen is produced if this condition persists for a few days, it'll be a disaster.
In these summer days, we blame the scorching sun endlessly, but if it goes into hiding , our survival will be at risk.