This phenology model/degree-day calculator uses weather data to calculate degree-days, also known as heat units that are used to estimate development of many organisms, such as insects and plants.

This app is a re-designed, mobile-friendly, member of a family of online model/calculators at: USPEST.ORG (home page). The numerous models served by this app are all driven only by daily maximum and minimum temperatures, using one of many different degree-day calculation formulas, many of which are described at this UC Davis IPM website. Note that this app requires an internet connection and will not work in airplane or off-line mode.

We split this app into tabbed sections in 1 or 2 rows near the top of the page. Use the tabs from left to right. This introduction is in the first tab, Intro. Notice while using this app, if you see the icon, click on it to access more explanatory information via a pop-up help window.

The second tab, Station, is where you select a source of weather data needed to run the models. This source is usually a weather station from our database, or it can be a file you upload.

Our station database contains around 29,000 weather stations from hundreds of weather networks throughout the U.S., with more in Canada and Mexico and some other surrounding places. Most of our weather data comes from Mesowest in Utah. We also have data from participating agricultural weather networks (scroll to far bottom of this page and read the fine print to see some of these).

To find a weather station, enter a known weather station code (e.g. ARAO), a zip code, or a city and state abbreviation. Then click on the button search for stations to find 1 or more expandable lists (click on + sign to expand, - to contract) of the 4-8 nearest stations. Once you click on a station code, you should see the text Selected station: with a station code and a place name. When you see this, you have selected a weather station. Be aware that not all weather stations are reliable, so you may need to return to this step.

You may also click on the (MAP) link to open a Google map selection option. With this, you can zoom in, zoom out, pan, and click a station pin to select a station.

If you want to upload a file, select Upload file (below the station search box, just above Next). You will need a file in the required format. Select the file, enter a label for your reference, select Celsius or Fahrenheit as appropriate, and click Upload.

Once you have a station selected, click on the next tab, Model. This tab begins with selection of a model category. For example, all models (ca. 139 models), insects (ca. 76 models), weeds (5 models), plant diseases (6 models), and crops (46 models), plus various combinations based on other criteria, such as invasive insects (27 models), apple and pear (16 models), stone fruits and nuts (12 models), etc. see current list.

Note that all categories include generic degree-day calculator as the first option; this is described below. Also note that none of these models are driven by hourly weather, only by daily max and min temperatures. See our list of apps at USPEST.ORG for hourly driven models, including most plant disease infection risk models.

Model Options

Once you have selected a model, you may need to change the dates.

Dates

Forecast Options

Temperature Scale Option

DD Calculator Options

Options not included in this version

Once a model is selected and options chosen, you may scroll down to review the model information, helping you confirm that you have selected the appropriate model for your needs. The Model inputs table includes information such as thresholds, region of known usage, model events, and links to extension pages and model source information. Many of the 100+ models were derived from one or more scientific publications and combined into a working model by OSU OIPMC in the form of a spreadsheet converted to PDF format.

Once the Station and Model have been selected, click on the Output or Graph tabs at the top of the page to see model predictions or output. The Output consists of:

Model Inputs table

Date Comparison table

The Date Comparison table shows you how the current year degree-day accumulation compares to those of recent past years and the 30-year normals. (Calculations use the current model inputs including the start date, threshold temperatures, and calculation method, but different years.)

For example, the table above was created on December 27, 2018, when 1377 DDs had accumulated since September 1st. In 2017, 1377 DDs had accumulated 23 days earlier (on December 3rd). In 2016, it took 2 more days (until December 28th) to reach the same total, and calculation using the 30 year normals did not reach 1377 DDs by the end of the year. (This example is admittedly somewhat contrived, but this could apply to e.g. fall-planted vegetables.)

The Date Comparison table is only available when the start date is in the current year.

Model Output table

The Model Output table is the main output from this app. It Each row describes a day, and has the day's date, temperatures extremes, rainfall, and degree-days. The row also has cumulative degree-days from the start date to the given day, and it may show data quality (QA) flags and model events.

The condensed version of the table, which is displayed initially, only includes days in which a model event occurs. In the full version of the table, there is a row for every day from the start date to the end date -- that is, all the days that used in computing the model.

Data Quality Assurance (QA)

Weather stations failures are common, and they are not always repaired promptly. Our system estimates values for any missing data, trying a number of different methods, and using the best one that succeeds. But estimated data are not as accurate as measurements, and less accurate model inputs lead to less accurate outputs. If you are concerned about a station's data quality, click "show full table" to expand to the full table.

When observations are missing, you will see a QA tag in the QA field. These tags are short strings indicating which estimation method was used, and each tag is a links to an explanation of the method. For example, Px indicates that the maximum temperature was estimated using PRISM map interpolation, and Hn indicates that a historical average minimum temperature was used. (When the QA field is blank, the temperatures are actual measurements.)

If you see numerous QA tags for dates in the past, you may want to run the model using a different weather station. (Click on the Station tab again, click search if necessary, and use the MAP link to see nearby station locations). If only a few of these tags appear, then you may expect little error in the degree-day accumulations. (Use at your own risk).

Observations are also unavailable for dates in the future. In this case forecasts are used as described above, and tags in the QA field indicate which forecast is used. For example, Nm reflects the use of NMME forecast data. Again, these tags are links to further information.

This tab presents model output as a graph, with dates on the x-axis and cumulative degree-days on the y-axis. Predicted model events are displayed both with reference to the degree-days as horizontal lines of text, and with reference to dates as diagonal lines of text starting along the x-axis.

Close-together events may overlap and be difficult to read. To help overcome this issue, the graph is interactive and allows for zooming in on the portion of the output you wish to see. Exactly how you zoom in depends on your device. Values will be shown when you when you hover over (or lightly touch) a graph line or point. You can turn off a data line by clicking on it's legend at the bottom of the graph.

The graph is plotted for the entire interval from start date to end date, but only the portion containing model events is initially shown. Clicking reset zoom in the graph will show the entire graph.

You will usually see several lines on the graph:

• If the model end date is in the future, a line will be plotted for each available “forecast”. Each of these lines will start where the observed data ends, so that you will see a range of possible futures. These forecasts are discussed above under Forecast options. For example:

  

• If the model end date is in the past, several “comparison lines” will be displayed as to provide context for the chosen year. Each of these lines will start at the start date. These lines may include the years before and after the chosen year and 10- and 30-year averages. For example:

  

Automated email delivery of the model outputs displayed in this app is available at no cost. An email subscription offers model results for these and other models, for multiple weather stations, on a schedule that you select. To subscribe, you will need a uspest.org account.

This app was funded primarily by a USDA NIFA CPPM EIP grant to support IPM at the state and regional level, and by the Oregon State IPM program at OIPMC. Other sources of support include other NIFA funded grant programs, including the Western IPM Center, and from USDA APHIS PPQ support.

Location search using place names (geo-coding) is by OpenCage, using data © OpenStreetMap contributors. IP address search uses GeoLite2 data from MaxMind.