So you come down to sunny, warm, Arizona for a golf vacation during the winter.  The daily temps have been hovering around 70 degrees, yet you go to the golf course and find they are telling you there has been an hour frost delay and your tee time has been moved back.  How can that be?  Well as crazy as it sounds, December through March Arizona Golf Courses are subject to frosty days, and our course is no exception to this.  

Many folks ask: Why does a little frost even matter?  The answer is that if everyone didn't want nice green grass and an even putting surface to play on, it wouldn't matter.  Unfortunately though, when turf grass freezes the liquid in the cells of the grass becomes ice crystals, and as we all know frost itself is ice crystals.  With any pressure from feet, cart tires, or any other weight bearing object on the frozen grass, the ice crystals from inside and outside the plant poke through the cell membranes causing any affected piece of grass above the root to die.  It takes several weeks in the middle of winter, even in Arizona, for the grass to grow high enough again that the mowers can cut off the dead section of grass.  So if someone walks on a putting green, fairway, or rough area, we end up with foot prints, cart tracks, and other such damage that shows for many weeks.  Below you can see examples of frost damage, the picture on the left is damage done from a maintanence vehicle on a golf course, the picture on the right shows a single set of foot prints walking across turfgrass, imagine what a foursome does on a green.


For some folks this may not matter, but trust me, standing behind the counter of the pro shop we hear plenty of complaints about course conditions, and if it looks bad people will go elsewhere to play.  In addition, here in Arizona we have to overseed during the winter to keep the course green.  This is a huge expenditure for the golf course, we spend $40,000 in grass seed alone, not to mention fertilizer and man power.  We will take whatever time is necessary to protect our investment.  We don't take frost delays lightly, they cost us thousands of dollars every year.  Every tee time that we don't send out in season costs us money (think your green fee times 4).  That's a lot of money to let go every seven minutes, but if a course gets a reputation for being a goat pasture it will lose way more than that in the long run.

So why does frost occur in Arizona when the temperature doesn't appear to be condusive to having frost? 

Unfortunately we are subject to a couple of conditions that actually make frost more likely to happen than in other parts of the country.  

1.  Desert areas are subject to big temperature swings.  It isn't unusual to see 30-40 degrees difference between the high and low temperatures for the day, so it may well be 70 degrees at 3 p.m., but only 35 degrees at 3 a.m..  Our typical clear night sky and low humidity doesn't capture any ground heat as it escapes through the night hours.

2.  When you have low air humidity and high ground humidity (example: a golf course with lots of water on it), as the water evaporates during the evening it makes the air dense and humid very close to the ground.  If an object on the ground reaches freezing level, for instance a blade of grass, it will freeze any water vapor in the air that comes in contact with it, creating frost.  We are in a very wet environment on the golf course so our ground humidity is considerably higher than other places, so we are more subject to frost.  

3.  In low humidity area's (i.e. Arizona), ground temperature can typically be as much as 7 celsius (that's 12.6 degrees farenheit) lower than the ambient air temperature at 6 feet above ground where most meteorological equipment is stationed.  It is actually possible to have frost when the ambient temperature six feet above the ground is 44.6 degrees farenheit because the ground temperature can be 32 degrees.  So when someone sees the weather report showing Phoenix is going to have a low of 40 degress, the actual temperature on the ground may well be 28 degrees.  I have seen days when people come into the golf shop reporting there is no way there can be frost because the temperature is above 40 degrees at their house, yet you can look out and see the golf course is white.  (See Pictures Below)

4.  It gets even worse.  Right when the sun comes up there are atmospheric conditions that take place that actually make it even colder at, or near ground level for the first hour the sun is up, and more condusive to frost.  As air cools down it becomes more dense and carries higher water volume, when the sun starts heating up the atmosphere the cool dense air is pushed toward the ground as the hot air rises, so it becomes colder at or near ground level in that first hour of sunrise than at any other point in the day.  All that dense humid air is down there where the frozen grass blades are so frost builds up even faster right as the sun rises.  

How long is the delay going to last?

I had a gal call me one morning asking how long the delay was that day since she was playing the next day and conditions were forecast to be similar so she wanted to plan accordingly.  I told her that the delay was about 40 minutes that particular day, but there was no way to predict how long it would be tomorrow.  She said, "Oh please, don't get me started", then she went on a rant about we should be able to predict frost delays and so on, and so on.  Funny thing, conditions were similar the next day, yet there was no delay at all.  I have no idea if she missed her tee time since I wasn't working the next morning, but she easily could have.

Honestly, there is no way to tell how long a delay is going to last.  Generally speaking, calling the golf shop is a waste of time, as we won't know how long the delay will be until the Grounds Crew calls and tells us the frost is gone.  Your guess is in all likelihood as good as ours.  There are so many variables that come into play that affect the length of a delay, such as humidity, ground temperature, cloud cover, wind, and ground moisture levels.  All of these vary from day to day and any combination can give us a whole new set of variables affecting the actual freezing, or lack there of.  For instance, all conditions being exactly the same, a 3 mile per hour breeze can mean the difference between a thick frost and no frost at all, or the difference between a 15 minute delay and an hour and a half.  Cloud cover can hurt or help, depending on when it builds.  If it is clear all night and the clouds build right as the sun comes up, which often happens, it will be a long delay.  However, if the clouds built up in the night time before the temperatures had a chance to drop, odds are there will be no frost at all.  There is no predictability when it comes to frost, everyday is different from the last.

If you have the ability to figure out how all the variables that create or disapate frost interact with one another to the point where you can tell us the severity and duration of the frost, please let me know because you are worth a lot of money.  Between the farmers and the golf courses I can help the two of us make a few bucks on the side protecting growing plants.

Frost delays are a burden for the golfers and the golf course alike.  Please be patient with us and understand that we can't predict when it will end and we can't make it go away any faster.  Below are a few pictures of our course under frost conditions.

Jan. 24th just as the sun comes up.

Jan. 24th, This thermometer was out for 15 minutes just as the sun came up (not in the sun), notice it is 40 degrees and we have frost.

For those who don't believe we have frost, the above were taken at Mountain Brook GC Jan. 24th, 2010.  These were taken about 8:00 a.m. near the practice green right in front of the Pro Shop.
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