From that article, it looks like if you were to inject a harmless, dead virus into your body, your body would largely ignore the harmless thing. An inflammatory adjuvant is added to the injection to purposely cause inflammation around the injection site, so the body associates the harmless virus with harm, thus developing immune memory.

So injecting most vaccines intravenously would spread the harmful adjuvant widely throughout your body, which is a risk you wouldn't want to take unnecessarily. Injecting into muscle is known to work well and be relatively safe.

What I always thought was that a single molecule of water might have enough energy to change phase, even if the temperature of "the water" isn't that high. The energy of the water molecules follows a bell curve with a long tail in the high energy end - the evaporating particles are in that tail.

https://physics.stackexchange.com/questions/521843/why-most-distribution-curves-are-bell-shaped-is-there-any-physical-law-that-lea

But wind has such a strong effect on the evaporation rate that I think this explanation must be lacking something. Do you have any insight?

Something with a high specific heat capacity needs more heat to increase its temperature by 1 degree.

Conductivity directly describes how much heat flow you get per difference in temperature.

They're related concepts but I think conductivity is the relevant one here. You feel colder when heat is drawn out of your body.

In cold weather our bodies lose heat mainly by conducting heat directly to the air. Moist air is a better conductor than dry air, so moist cold air feels colder.

In warm weather, we mainly cool ourselves by sweating. The sweat evaporates, which is an endothermic reaction which takes heat out of your body. When the air is already saturated there's little evaporation, so this process stops working. So moist hot air feels hotter.

So humidity makes extremes of temperature more extreme - hot gets hotter, cold gets colder.

(edit) People have pointed out a mistake. The humidity of cold air is always low. The difference in conductivity between cold air of high relative humidity vs cold air of low relative humidity is negligible, as displayed in this graph. https://www.electronics-cooling.com/2003/11/the-thermal-conductivity-of-moist-air/

Some people are sharing anecdotes that they feel much colder in more humid weather - I think that's more to do with moisture on your body than moisture in the air.

(edit) Some people want to note the detail that evaporation is a phase change, not a chemical reaction.

As you add heat energy to water, its temperature increases linearly until it gets to about 100 degrees C. From here it takes in additional energy, but its temperature doesn't rise - this energy is instead used to break its bonds to complete the phase change from liquid into gas. Once the phase change is complete and it has become a gas, you see a linear relationship between heat and temperature once again.

So what's happening is you're transferring your body heat into the sweat, which is evaporating and carrying that energy away.

https://socratic.org/questions/how-can-i-calculate-thermochemistry-equations-for-phase-changes