Writing 2

你好。
今天是星期日（一般说星期天，星期日也对，但是星期天比较常用）。今天天气雨。昨天天气雪。
下星期五我有考试。我必须学习。

谢谢。

Writing 2

你好。
今天是星期日。(It is correct , but we prefer to say 星期天instead of 星期日）

今天天气雨。（It is correct , but if you want to say in a native way, "今天是个雨天"is perfect，it meas today is rainy day .

昨天天气雪。(Same as last sentence ,"今天是个下雪天"，it means today is snowy day.) 

下星期五我有试。（“试”is a verb means try/test, "考试"is a noun means exam. They are different.)

我必须学。(Actually , Chinese sentence rarely finish with a word incudes 1 character ,so you'd better use "学习“instead of "学", there is a good explaination of this using habit . Website: http://forum.wordreference.com/showthread.php?t=2919307）

谢谢。