Uncomfortably means in a way that causes unease of body or of mind. Something is wrong and you cannot settle.
The physical sense covers heat, chairs and shoes. The commoner use is about a feeling, and uncomfortably close, uncomfortably aware and uncomfortably familiar all describe something that is troubling precisely because it is nearly right. That second use is where the word earns its keep in writing. The adjective uncomfortable covers both, and the noun discomfort is what a doctor asks about.
1adverbuncomfortablyIn a way that causes physical or mental unease.
“The room was uncomfortably hot.”
2adverbtroublinglyIn a way that is troublingly close to the truth.
“The description was uncomfortably accurate.”
From uncomfortable + -ly or un- + comfortably.
Etymology from Wiktionary, CC BY-SA