I've had similar problems with my AM2315. A few times a day it will either return a CRC of -1, or a temperature value that's a large difference from the last reading. Sometimes the difference is small, like 10 degrees, and sometimes it's hugely different, like -2800 degrees. And sometimes it will run an entire day without any problem whatsoever.
I worked around this by modifying the code in GroveWeatherPi.py to remember the previous temperature and retry if either the CRC is -1, or the temperature difference is more than 5 degrees. I set it up to retry up to 10 times. I'm also syslogging when this happens so I can check on the frequency of the problem. So far it's been running 3 months and has never had to retry more than 7 times.
I've also noticed that the sensor gives reasonable readings when the temperatures are around 0C or above, but at lower temperatures it seems to read up to 5 degrees higher than measured with a digital thermometer. For example at outside temperatures of -20C, it might read -14C.
We need to get a better idea of what you are doing so we can help you. Please give us a picture of your setup and tell us what software you have installed and what you are running. Give us the screen shots too.
Remote debugging is hard! With more information we can definitely help.