Ответ:

1) I'll lend you an umbrella unless you have one

2) You'll get wet unless you take an umbrella

3) He'll fail his exam unless he studies

4) I'll be very disappointed unless he studies

5) Will it be alright unless I wear a tie?

6) They won't let you in unless you have a tie

7) Tourists will be happy unless it rains in August

8) There will be water shortages unless it rains this August