Yes, CONDITIONS is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, N 1, D 2, I 1, T 1, I 1, O 1, N 1, S 1.

Is it a valid word?

CONDITIONS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the prevailing context that influences the performance or the outcome of a process
the set of circumstances that affect someone's welfare
the atmospheric conditions that comprise the state of the atmosphere in terms of temperature and wind and clouds and precipitation
a state at a particular time
an assumption on which rests the validity or effect of something else
a mode of being or form of existence of a person or thing
information that should be kept in mind when making a decision
the state of (good) health (especially in the phrases `in condition' or `in shape' or `out of condition' or `out of shape')
an illness, disease, or other medical problem
(usually plural) a statement of what is required as part of an agreement
the procedure that is varied in order to estimate a variable's effect by comparison with a control condition

establish a conditioned response
develop (children's) behavior by instruction and practice; especially to teach self-control
specify as a condition or requirement in a contract or agreement; make an express demand or provision in an agreement
put into a better state
apply conditioner to in order to make smooth and shiny

Also: weather condition, atmospheric condition, experimental condition.