Tuesday, March 5, 2013

Wild Temperature fluctuations mean it’s Spring in Tucson

Monthly Average Temperature for Tucson
The desert areas in Pima County, Arizona experience extreme weather most of the year. In relation to Tucson, it is safe to say that Spring consists of 2 weeks in March in which the temperatures are consistently between 75 and 90 degrees Fahrenheit. To hope for more than a short spring is just wishful thinking. Though graphs may say that the average temperature is more slow in changing, the actual change between the high 60-70 degrees of winter and the high 90-100 degrees of summer is very short - especially in the spring.

So what happens in Tucson’s spring? The mesquite trees begin to grow out their first leaves, insects start hatching, and gardeners keep growing their winter crop while hoping that they can begin their summer crop without having it freeze on one of the last cold nights of the season.

Average Hours of Sunshine per day
When is “all danger of frost” gone in Tucson? To answer this question I prefer to use the measure of what we call a “false start”. These usually occur in March. A false start begins when the temperature warms up for the first time in a while. There are no more freezing nights and everyone thinks summer is right around the corner. This weather pattern continues for about 2 or 3 weeks, and then the temperature drops and it freezes one last time. The deceptive first warming spell was called a “false start”. Beginning gardeners then realize that it wasn’t quite time to put those plants or seeds in the ground and that the cruelty of the desert climate requires gardeners to learn quickly.

After the last freeze – usually an outlier over the last 3-4 weeks – it is generally safe to plant the first of the frost sensitive plants. However, even after that point I still continue to use milk jugs filled with water to keep plants safe when temperatures drop to close to freezing. The water in the milk jugs protects the nearby plants via radiant heat. Radiant heat is helpful when outside temperatures are fluctuating wildly in the spring but can completely destroy my plants as summer-like temperatures approach. As soon as the outside temperatures rise above 90 degrees I remove all my milk jugs to keep plants safe and provide them with more room to grow. Concerns with radiant heat was one of the reasons why I was forced to plant my garden away from block or brick walls, which would otherwise cook my plants during Tucson’s summer days (and nights).
Radiant Heat is helps during temperature fluctuations

So, should you want to visit Tucson I would highly recommend coming in March. It is beautiful here now – though you will still need a jacket when it gets dark out. As much as I enjoy gardening here, extreme heat can really gnaw at you in the middle of the summer. As the Arizona summer bears down on us I’ll be wishing I was someplace north.

It's Spring here in Tucson


  1. I lived in PHX 2 years as I went to school and I moved back east because the summers were just too HOT!! Loved the short spring though :)

  2. Florida often has those false starts in March, too. Not this year, tho. Still cold and windy here. Really cold at night, warms up during the day. We had a serious false start in December, which, of course, fools no one and all the plants thought it was spring!


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