i would recommend to use espimatic instead of running a complete pi for measuring temp / hum.
for that you need an esp8266 with 4MB flash such as Wemos D1 or NodeMCU or ESP12
for the actual setup you can use the pimatic api (if using pimatic on both pi’s) to push the data from one pi to the other. another possibility would be to write the dht data into a logfile, then mount the directory with the log in it on the pimatic pi and read the data with the logreader device.
another possibility would be to curl the logfile or maybe the dht sensor directly with a shellsensor device.