Accurate weather information is crucial for those working in the tree care industry. Trees, like all plants, must be suited to exist within the range of weather conditions at a given location. Although there’s some adaptability, a particular tree species can generally thrive in certain environments but fail in others. In addition, coping with tree damage is a major component of tree care. Severe weather conditions produce much of this damage. There’s also the human factor — in outdoor work, conditions need to be favorable and safe for people to get the job done.
A variety of weather information sources are available, including from several private firms. The official source of all weather information is the federal government, more precisely the National Oceanic and Atmospheric Administration — much of its information is free and readily available online. For the U.S. and much of the rest of the world, the NOAA collects pertinent weather information and produces useful resources and timely forecasts.
Keep in mind, there’s a difference between weather and climate — and each is important. Weather refers to the current conditions, for example temperature, humidity, etc. We use weather predictions out as far as one year (for example, the weather of 2016). Beyond that, we use climate, which refers to past conditions. Typically, we talk about averages over longer periods of time; 30 years is the standard. But beyond just averages, climate data also highlights the weather extremes that have occurred in the past. Often, it’s the extremes that are useful in future planning.
Tree care specifics
The type of trees that naturally occur in a region are compatible with the climate; in particular, the temperature and moisture conditions. In fact, climate types are often defined by the type of trees that grow there, if trees occur at all.
If you’re selecting tree types, you need to know their climatic tolerances. Then you need to know as much about the climate of your location as possible — not just the average conditions, but also the extremes that may well exceed tree tolerance.
Climate data for the U.S. and many other countries is collected and processed at the Center for Weather and Climate, which is part of the National Centers for Environmental Information located in Asheville, North Carolina. For your location, you can look up the average temperature and precipitation. You can also see seasonal differences. How hot does it get in summer? How cold in winter? Are there wet and dry seasons? You can also check on record temperatures. What extremes may a perennial plant face? If frost is a concern (say for fruit trees), there are several products that give you dates and probability of occurrence. All of this information can be compared to tree requirements.
If you’re a local, you probably have a good idea of your climate. But this data gives you specific values you can use. If you’re new to a region, a look at climate data gives you a good idea of what you’re dealing with.
Climatology can help with planning, but in terms of dealing with tree damage or doing outdoor work, you’re concerned with the current weather and the forecast. The official source of weather in the U.S. is the National Weather Service (NWS). If you go to its website and click on your location on the interactive map, it will take you to your local NWS office. There you can find all types of information on the weather from the past, present and future. The standard forecast will include temperature, wind direction and speed, sky condition (sunny, cloudy, etc.) and precipitation (if any is expected). Although the standard written forecast covers 12-hour periods, there are digital and graphical displays that depict expected hourly changes in these variables.
For outdoor work, the occurrence of precipitation is a major factor. The precipitation forecast has two components: the probability of precipitation (PoP) given as a percentage, and the expected amount of precipitation during a given three- or 12-hour period. A couple of things to keep in mind about the PoP — it has no relation to the expected amount of precipitation and no relation to real coverage of precipitation. A PoP of 40 percent means that any one location has a four in 10 chance of precipitation, not that 40 percent of the forecast area can expect precipitation.
Dealing with extremes
Worker safety is a major concern as inclement weather poses a variety of risks. Temperature extremes can cause illness, which can be serious in some cases. In the winter, a combination of low temperatures and wind can cause a dangerous amount of heat loss from your body. Anything from frostbite to fatal hypothermia can occur. The wind chill factor combines these two elements into a single apparent temperature — one that you feel. A wind chill warning can be issued if conditions warrant, typically with wind chills of minus 20 degrees or lower (specific criteria vary by state).
In summer, it’s the combination of high temperatures and humidity that causes concern. The heat index combines these two factors into one apparent temperature. A heat advisory is issued typically if the heat index is 100 degrees or more. An excessive heat warning is issued when the heat index exceeds 104 degrees. Again, these values will vary somewhat by location.
The greatest threat in the spring and summer comes from thunderstorms, which bring weather issues including strong winds, large hail, flooding rains and even tornadoes. Dangerous lightning is inherent with all thunderstorms. The possibility of thunderstorms will be highlighted in any forecast. A NWS severe thunderstorm warning implies the immediate potential for damage.
The best tool for following thunderstorms is weather radar. In today’s world, finding this data is simple using computers, tablets or smartphones. There are also numerous apps that have weather radar. Thunderstorms typically show up as bright red and can be tracked. The tried-and-true rule on thunder still works: if you see lightning and start counting until you hear the thunder, the strike was a mile away for every five seconds that pass. If a storm approaches, get indoors as quickly as possible. A house or substantial structure is safe; something like a shed isn’t. The inside of the cab of a car or truck is safe; an open-cab vehicle like a tractor isn’t. Certainly, stay away from trees. Taller objects make a shorter and easier path for lightning bolts. Side bolts can jump from the trunk of a tree and dangerous electrical current can travel under the ground.
Wind is especially important for those working above ground. The standard forecast will give you expected wind direction and speed with peak gusts. The NWS can issue a wind advisory, or a high wind warning, for unusually strong winds.
In terms of tree damage, strong winds are also a major factor. Typically, most large-scale wind events occur with fronts or winter storms. If you’re in an area that may be impacted by tropical cyclones, these strong winds are infrequent but can occur in the late summer or fall. Check the National Hurricane Center for the latest forecast.
Helpful Weather Resources
- Center for Weather and Climate (formerly the National Climatic Data Center)
- NOAA: Regional climate centers
- American Association of State Climatologists