Thursday, May 29, 2014

Oddities about Wednesday Night's Minimum Temperature "Record"

Wednesday night was remarkably warm, with an overnight low at the Salt Lake City Airport of 74ºF, good enough for a record high minimum temperature for both the day and the month, or was it?

Source: NWS.
As noted in the NWS statement above (see the * and +) records at the Salt Lake City airport are based on the calendar day (i.e., midnight to midnight).  As such, the low temperature for the day can occur at any time during that period.  So what happened before midnight last night?  There was a cold-frontal passage just before midnight, but temperatures remained quite high, dropping to only 73ºF by midnight.  Still good for a record right?  

Nope.  The calendar day is defined using standard time and we are currently on daylight time.  Midnight standard time is actually 1 AM daylight time.  By 1 AM, the temperature fell to 67ºF and that stands as our official non-record minimum for the day.  

Easy come, easy go.  Even the 93ºF maximum wasn't a record.  It would have tied the record the previous day, but in 2003 we hit 99ºF on May 28th.  

Source: NWS
So, we were shut out all around, but it was still a very warm day that ends up being 16ºF warmer than average.

1 comment:

  1. I have always thought it would make more sense scientifically to use the actual overnight minimum values... perhaps the lowest value between noon on a given day and noon on the next (or the equivalent in daylight time). But I guess someone decided on the calendar day method long ago. Is there any variation in how this is computed at different stations, or perhaps in other countries? Just curious.