Lately I've been discussing about the temperature inside a shed with a friend. Due we had no thermometer, we couldn't check our intentions.
So how could we improvise a thermometer next time? We can use anything you can find in general households.
There's a pretty simple way to build your own thermometer with household items. Though it can only show temperature changes. If you really want to know how much degrees the temperature changes you'll need to calibrate your self-made thermometer with a real thermometer.
What You Do:
If made as explained above, you will only see temperature rises. To also see falls in temperature you need to add a few drops of your red mixture to the straw.
On wikihow there also are some useful tips:
As far as I read through the instructions on the linked sites, this isn't intended for air measuring. I guess, if you don't want to measure small temperature changes this will work for air measurement as well.
You can improvise a thermometer with 4 simple ingredients that can be found in most households:
Now what you can do is put a few drops of food colouring into your water bottle and fill it up to the top with lukewarm water.
Then insert your clear (non-bendy) drinking straw a couple of inches into the top of the bottle and then mold your clay / putty (play-dough would work) around the straw and the top of the bottle until you have an air tight sort of lid with a straw coming out of it. (Be careful not to squash your straw as it needs to be free to pass liquid)
Use a marker to mark on the level of the water in the straw (assuming room temperature). You can then put it in a bowl of hot water and the water in the straw should rise and you can now mark on this temperature.
Similarly with some ice-water, the level of water in the straw should decrease and you can mark this on the straw too - the fact you have no thermometer makes it hard to know exactly what temperature these markings are at but you can know if it is 'ice-water' cold or 'boiling water' hot.
If you set this wherever you need it, you'll have a rough idea of what the temperature is in the room.
Note that water isn't that quick to respond to temperature changes so you can make it a 50/50 solution of rubbing alcohol and water and this should give a slightly quicker response.
This link gives and explanation as to how it all works if you are interested!