Dry Buster

A week ago much of Minnesota and some portions of eastern North Dakota were listed as either abnormally dry or in minor (D1) drought conditions.  That changed quickly last week in central and eastern Minnesota when 3-5 inches of rain fell prompting flood warnings to be issued.  Yet, that system stayed to our east keeping the local area dry and still waiting for rain.  Our turn came on Saturday Night into Sunday morning when much of west central Minnesota recorded 2-4 inches of rain with localized higher totals.

Fargo Moorhead ended up right on the edge of that system with much of Moorhead receiving over 2 inches of rain, where as parts of West Fargo up towards NDSU only recorded near 1 inch.

It was a reminder that our wet phase is likely not over and we continue to be just one heavy rain system away from being over saturated with flooding problems once again.

Frosty Night

Last year, Fargo officially dropped down to 33 degrees on May 26.  It appears we will once again see a late season frost as temperatures tonight may also drop in the to 30s.  Below is my projection for low temperatures at numerous cities in the area.

One thing in our favor tonight will be soil moisture.  Many spots received quite a bit of rain Sunday morning.  That soil moisture will help hold temperatures up a bit near the surface for emerging crops, yet, it could be a close call in low spots in particular.

When Will the Streak End?

A year ago, Fargo Moorhead had yet to hit 80 degrees.  That would come on Memorial Day which was on May 30th last year.  May 2011 would be our 6th straight month with below average temperatures with all of those months, with the exception of February, finishing with above average precipitation.   June was certainly not a hot month last year, but it did finish 0.8 degrees above average, granted, that would be considered an average month, but it was still a change from the cold pattern that had dominated the region for several months.

The summer would go on to be slightly above average, including the month of September, but from October to the present day, with a few exceptions this area has recorded temperatures well above average.  This pattern will probably come to an end in the upcoming months, with perhaps a slow decline to normal, then a period of below average temperatures, which would mean our string of warm autumns could be ending this year.

90 Mays

A 90 degree high temperature in May occur approximately every 3 years.  Before this month, the most recent years with a high at 90 degrees or higher in Fargo Moorhead were back in 2010, 2006 and in 2001.  Although temperatures that warm have occurred in only 46 Mays, everyday of the month, but one, has a record high of 90 degrees or higher.  The exception is May 6 that has a record high of 88 degrees set back in 1896.

Although a few days in the 90s in May is not that usual, what has been historically rare has been temperatures in the triple digits.  Since 1881 there has only been two recorded days when the high temperature reached 100 degrees or higher.  By coincidence, both times were on May 30, one in 1934 and 1939.  So if you have a 2012 StormTRACKER calendar you will notice only one record high this month above 100 degrees, a 104 degree high on May 30, 1934, but in 1939 there was another scorcher of 101 degrees on that very same day.

ET Measurements

Evaporation is simply the process of liquid water being converted to water vapor.  If this process involves plants, then it is referred to as transpiration.  The amount of water evaporated into the atmosphere varies not only from season to season, but also on a daily basis.  Last year, North Dakota State Climatologist Dr. Akyuz acquired an Evapotranspiration Simulator (ETGage) which measures the amount of evaporation taking place each day.

This past Monday and Tuesday when the temperatures were in the 80s with dew points in the 20s the ETGage measured an evaporation loss of 0.65 inches over those two days.  The dry air in combination with nearly 100% sunshine and a good wind made for an ideal evaporation environment.  On the opposite extreme was May 8 when only 0.02 inches of evaporation loss was measured because of the combination of a light rain, cloudy sky and high relative humidity.

Dr. Akyuz reports his data on cocorahs.org if you want a better sense of water loss during the growing season.

Flower Trouble

Abnormally warm springs have advantages and disadvantages.  The warm weather allows for earlier planting, the rebirth of spring to occur ahead of schedule and there is just the overall pleasure of the warmer temperatures.  But there is one noticeable disadvantage, frost.  The record breaking warm March in combination to an above average April induced many plants to bud out much earlier than usual.

Many of the flowering trees and other plants have already bloomed. Yet, depending on the species, some plants did not flower at all this year.  For instance, several lilac bushes did not and will not bloom this spring.  As the buds were coming out, we had a cold snap in mid April when temperatures dropped into the teens one morning.  Plus, some of the plants that were already flowering during that stretch will not produce fruit.  Someone living near me mentioned his apple trees will not produce any fruit this year.

A premature warm up is often a concern in regions to our south, but this year we experienced what southern fruit farmers fear every year.

Back to the 80s

The 83 degree high temperature this past Thursday was the first 80 degree day of the year.  The long-term average for such an occurrence is May 6 so it occurred right near the average.  Last year Fargo Moorhead did not record an 80 degree temperature until May 30 which almost made May 2011 the first May since 1983 without an 80 degree temperature.

Locally we average five 80 degree days during the month of May.  The year with the most days with temperatures in the 80s or higher occurred back in 1977, which was also, unsurprisingly, the warmest May on record and by a significant margin.  It is interesting to note that the summer of 1977 finished with below average temperatures meaning the warmth of May did not translate into a warm summer.  Yet, other years with early heat in May, like 1988 and 1936 maintained that heat through the summer months.

Although this year has only recorded one warm day so far, it appears more are on the way next week.

It is Your Latitude

The climate in this area is dominated by two factors; our continental location and our latitude.  Although not recognized by the United States Geological Survey, the area around Rugby, North Dakota is considered by many to be the geographic center of North America.  This means that we live about as far away from an ocean as you can get in the Western Hemisphere.  Without the modifying influence of a nearby ocean our temperatures fluctuate wildly during the year.

Our other great climatic influence is our latitude.  When I go to area schools and talk about the weather, the word latitude almost always is a part of my presentation.  Through the years I have always been amazed at how few students know what our latitude is locally.  But Fargo Moorhead lies near 47 degrees north latitude, meaning, we are closer to the arctic than we are to the tropics, which, when combined with our location in the center of the continent, helps explain why our climate would be considered by most to be a cold one.

The Last Frost

From 1881 through 2011 the average last frost in Fargo Moorhead was May 13.  The current 30 year average (1981 through 2010) is May 8.  Using either average, this tends to be the time of year when we record the last freezing temperature of the season.

For those of you familiar with statistics, the standard deviation is 12 days, which in simple terms means there is a window of about three weeks when the occurrence of that last frost would be considered “normal”.   Of course, three weeks in our climate can easily mean the difference between a great crop or no crop at all.  Plus, all these stats are based on a 32 degree temperature, but frost does occur with temperatures warmer than the official measurement and if you use 34 degrees that normal range extends out to nearly one month.

This makes it difficult to know when to plant, but the reality is, in our climate if you wait until it is safe to plant, you would never plant, so at some point, you just have to play the odds.

Our Rainy Season

May in some ways could be considered the start of our rainy season. Climatologically, Fargo Moorhead is quite dry from November 1 through April 30. That six month stretch averages just 5.8 inches of rain and melted snow with nearly half of that falling during the months of March and April.

With recent years recording above average rain and snowfall, our perceptions may have changed, but what we have experienced in the last six months has been very average from a historical perspective. Both March and April average around 1.3 inches of rain, but this month, that average jumps to 2.81 and in June we average nearly 4 inches of rain.

In total the next six months the average rainfall is nearly 17 inches. Looked at another way, about 75% of our yearly precipitation comes from May 1 through October 31. So although our climate does not have a true rainy and dry season, an examination of the data hints that we almost could consider ourselves in the category.