How is the weather in Beijing from Apr 1 to 08? Is it safe in Beijing due to the radiation in Japan?

We are planning to go to beijing on this coming 1st to 8th April. How's the weather? What is the average (celcius)? Is it safe with the current situation at Japan related to the rumors on radiation. I have heard about the beijing people being cautious, buy the salt and etc. As this is the first time we go there, for sure we will be exploring Beijing and being outside all the time. Please give your opinion about it. Thank you.