Sensirion Temperature/Humidity sensors are some of the finest & highest-accuracy devices you can get. The SHT41 sensor is the fourth generation of I2C temperature and humidity sensor from Sensirion. (They started at the SHT10 and worked its way up to the top!). The SHT41 has an excellent 1.8% typical relative humidity accuracy from 25 to 75% and 0.2 °C typical accuracy from 0 to 75 °C. Note that compared to the SHT40, the SHT41 has the same typical accuracy of 1.8% RH from 25-75% but has much better accuracy over the full humidity range, with a typical accuracy of 2% over the 0-100% RH range, whereas the SHT40 has a worst-case typical accuracy of 3%. Also, the SHT41 max accuracy is 3% where as the SHT40 has a max accuracy of 6%. So basically, you'll get better accuracy for not-much-more cost.