You really do want 5/30 in it but one time probably won't do any real damage. The weather up there is above freezing by now isn't it? If not, I would consider draining the 10/30 and putting 5/30 in it right away.
The engines in our cars were designed for thinner oil and you could have problems with the thicker stuff. Ford even recommends that 5/20 is appropriate.
