user70567: I have 2 IoT devices for measuring room temperature. Room does not have direct sunlight (it is north oriented and have tree in front of window). One is ESP8266 with DHT11 and next one is ESP8266 with DS18B20. DHT is on the table, away from PC. DS18B20 is on the top of bookshelf next to plant. Both of them shows temperature around 32-33 deg. celsius. It is not that hot in the room for sure. My home thermostat shows 23-24 deg. celsius. Outside temperature is about 15 deg. When I open the window and cool down the room, I can see temerature drop on both sensors, but still ony to around 26-28 celsius. I think, they are overheating themselves.
Code is almost same on both devices. Sampling every minute, so it should not be an issue of overloading sensors. Supply voltage is 3,3V. Not parasitic with 2k2 pull-up resistor.
What should I do to get correct temperature reading from these sensors?
EDIT: I have tired to get sensor out of PCB. First, I have just raised it for lengt of its legs (about 1cm) above board. It helped little, but it is visible, that sensor started cold, and slowly saturated heat from wires. So I took quite thick cables (0,25mm^2) and put sensor about 10cm away from board. And it helped! Temperature is about 23 degrees, what is somwhere in expected range. Most important is, that temperature curve was dropping before stabilizing. Spikes are just 85°C first reading. 

user70567: It seems, that problem is in heat transfer from ESP chip to thermometer via wires. Worst it was, when chip was on board itself, little bit better when it was raised about 1cm out of board. I have achieved correct readings only when I put sensor on longer and quite thick leads to avoid heat transfer as much as possible.

70567: <p>I have 2 IoT devices for measuring room temperature. Room does not have direct sunlight (it is north oriented and have tree in front of window). One is ESP8266 with DHT11 and next one is ESP8266 with DS18B20. DHT is on the table, away from PC. DS18B20 is on the top of bookshelf next to plant. Both of them shows temperature around 32-33 deg. celsius. It is not that hot in the room for sure. My home thermostat shows 23-24 deg. celsius. Outside temperature is about 15 deg. When I open the window and cool down the room, I can see temerature drop on both sensors, but still ony to around 26-28 celsius. I think, they are overheating themselves.</p>
<p>Code is almost same on both devices. Sampling every minute, so it should not be an issue of overloading sensors. Supply voltage is 3,3V. Not parasitic with 2k2 pull-up resistor.</p>
<p>What should I do to get correct temperature reading from these sensors?</p>
<p>EDIT: I have tired to get sensor out of PCB. First, I have just raised it for lengt of its legs (about 1cm) above board. It helped little, but it is visible, that sensor started cold, and slowly saturated heat from wires. So I took quite thick cables (0,25mm^2) and put sensor about 10cm away from board. And it helped! Temperature is about 23 degrees, what is somwhere in expected range. Most important is, that temperature curve was dropping before stabilizing. Spikes are just 85°C first reading. <a href="https://i.stack.imgur.com/oKag6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oKag6.png" alt="enter image description here" /></a></p>
 70567: <p>It seems, that problem is in heat transfer from ESP chip to thermometer via wires. Worst it was, when chip was on board itself, little bit better when it was raised about 1cm out of board. I have achieved correct readings only when I put sensor on longer and quite thick leads to avoid heat transfer as much as possible.</p>
