B737-700
Other Deadheading pilot
Flight Crew Last 90 Days 184
Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
General Flight Cancelled / Delayed
Human Factors; Weather
I was deadheading on the flight sitting in a window seat overlooking the left wing. The window shade was closed to keep the aircraft cool during boarding. When we started taxiing out I opened the window shade and observed cold soaked fuel frost (CSFF) covering about half the wing; to include a significantly coarser; thicker frost area in one section. I notified the FA; and asked her to notify the Captain. The Captain stopped the aircraft and came back to observe the frost. Shortly after he went back to the flight deck; the flight was put on a ground delay for 30 minutes due to weather. During this period the frost melted. The Captain did return prior to departure to check the wings again.The previous flight was greater than two hours and the humidity was high in the ZZZ area; although the temperature was also in the 80's F. Due to the weather in the ZZZ area I am sure there was plenty of alternate fuel on the [inbound] leg.Upon exiting the aircraft I walked past the Captain in the jetbridge and he looked at me and turned away. He looked angry and annoyed that I had made him aware of the CSFF. Most professionals would say thank you for ensuring we didn't take off with frost on the wings. My concern is that maybe some crews are forgetting about how susceptible the 737-700/-800 is to CSFF; even in the summer. Additionally; I am concerned that maybe some pilots don't think it's a big deal to depart with CSFF.
Deadheading pilot reported notifying the flight crew during taxi out of cold soaked fuel frost on the wing surfaces that had presumably gone undetected during preflight.