I want to study how some certain parameters affect sensors of different manufacturers. To study any possible interactions, e.g., in lm in R, it is possible to study these interaction effects via

lm(Response ~ (rH + T)^2, data = df)

with the Response to the predictors relative humidity and temperature. I'm in the weird situation now, that relative humidity rH and temperature T have a strong influence on both sensors while the interaction term has also a strong influence on the one sensor and on the other not at all.

How do I interpret this? Even in general, how to treat interaction terms? When, in my case, humidity and temperature have already an influence, is there any (physical) meaning for their interaction?