For small plants, just say the first three weeks a temperature of between 20 and 25 degrees is ideal. After three weeks the temperature is allowed to go up some degrees. It is important that the temperature does not fluctuate too much. So try to take care the temperature does not drop too much at night, especially for small plants this could be disastrous.
A humidity between 40 and 60 percent is ideal for the cannabis plant in the flowering phase. This can easily be measured with a cheap thermometer and hygrometer. In the growing phase (first 6 weeks) it is best for the weed that the humidity is as high as possible.