Make yourself a schedule - e.g. no housework after 11 am. That way you have the afternoons free to do holiday type activities.
If it were me, I would
- go to local sites of interest, as Calliestemon suggested. Join a guided walking tour of your home town, visit a museum
- go to the cinema.
- go to a concert - there are lots of summer festivals on at the moment, some involving picnics in parks
- Just make yourself a picnic and go and eat it somewhere nice.
- Take yourself to a cafe for an ice cream. People-watch, Read a book, write a letter whilst you're sitting there.
- Take a bus or a train to somewhere you don't go to very often and take yourself for a walk
- Go for a cycle ride
- Go to a zoo, or something that you would normally only do with children.
- If the weather is nice, don't bother with the TV. If you want to spend the evening at home, listen to the Proms on Radio 3 or watch a DVD or read a book.