More than plausible, for 8am on a January morning! I used to ride a motorcycle every day from the Haight (home) to the Financial District (work), and the tempe

More than plausible, for 8am on a January morning! I used to ride a motorcycle every day from the Haight (home) to the Financial District (work), and the temperature grade changes were palpable. Your point is also completely correct, of course. :)