During the Christmas season, aviation weather reports often feature festive " Easter eggs." While some are actual remarks (RMK) added by Air Traffic Control (ATC) or meteorologists to official reports, many popular jokes are injected by flight planning software like ForeFlight to add holiday cheer. 

Common Christmas TAF and METAR "Remarks"

Pilots frequently share these humorous weather codes during December: 

Santa Activity: SANTA IN VCTY OF APT (Santa in the vicinity of the airport).

Festive Weather: PSBL SMK - CHESTNUTS ROASTING (Possible smoke from chestnuts roasting).

Operational Advisories:

RED REINDEER NOSE USE PROHIBITED ALL TAXIWAYS.

CAUTION GRINCH ACTIVITY INVOF ARPT.

MAGIC REINDEER DUST reported as a weather phenomenon.

Behavioral Reports: COAL IN VCT OF NAUGHTY. 

The "Santa's Checkride" Joke

Beyond coded weather reports, a staple of FAA Christmas humor is the "Santa's Checkride" story. In this joke, an FAA examiner arrives to perform Santa's annual flight review. After checking the sleigh and the reindeer's weight and balance, the examiner climbs in with a shotgun. When an incredulous Santa asks why, the examiner replies, "I'm not supposed to tell you this, but you're going to lose an engine on takeoff".

Weather:

Today

Cloudy, with a high near 37. Northeast wind around 5 mph becoming south in the afternoon.

Tonight

Mostly cloudy, with a low around 29. South wind around 5 mph becoming north after midnight.

Christmas Day

Mostly cloudy, with a steady temperature around 32. North wind around 10 mph becoming east in the afternoon.

Thursday Night

A chance of snow showers after 1am, mixing with freezing rain after 4am. Cloudy, with a low around 23. Southeast wind 5 to 10 mph, with gusts as high as 25 mph. Chance of precipitation is 40%.

Friday

Snow showers and freezing rain, mainly before 1pm. High near 33. Southeast wind 5 to 10 mph, with gusts as high as 25 mph. Chance of precipitation is 80%. New snow accumulation of less than a half inch possible.