1.they intend to have a picnic on the weekend
=they are having a picnic on the weekend.
2.my sister's hair is long and curly
=my sister has a long and curly hair.
3.the weather is too bad for us to go out
=the weather isn't nice enough for us to go out.
4.the coffee is so hot that my father an't drink it
=the coffee isn't cool enough for my father to drink.