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Where can I find historical rainfall data?

Where can I find historical rainfall data?

Historical rainfall data is easy to obtain from various sources, but the best options differ depending upon your needs. Below, we’ll help sort through the options to find the easiest and best way to obtain historical rainfall data for your project.

Single Location and Single Date

If you need historical rainfall data for only a single location and a single date, you can use a weather history page such as Weather Underground. For example, the following URL will give you weather history data for Herndon, VA.
https://www.wunderground.com/history/daily/us/va/herndon

Simply select the specific date in which you are interested, and the metrics on the page will update to show the weather on that date. To find the rainfall on that date, scroll down the page until you see the precipitation section.

Weather in Herndon,VA using Weather Underground
Weather in Herndon,VA using Weather Underground

There are few positive features to note about this method. First, the data is presented on a web page that shows a few nice graphs and tables to be very human friendly. If you are not distracted by the large areas dedicated to flashing ads, this option is quite visually appealing. Another positive feature is that you can chose a nearby weather station if you prefer. Although rare, in some cases you may have knowledge that a specific station is closer to your desired location or more accurate for some reason. If so, you can click on the “Change” option below the location name header to pick an alternate station.

Another valuable feature is the ability to aggregate the weather data at the week or month level. You can select this via the range selection options below the date selector. Note, however, that this does not work for all stations. Indeed, this option and various other history options only appear to apply to more major stations such as those at airports. So, if you find some of the history functionality not working, you may need to use the station “Change” option to pick a better session.

There are also some negatives related to this method. One primary limitation is the inability to load more than a single location or single date easily. If you need data for multiple locations or dates, this process will become tedious very quickly. Another limitation is that you cannot easily extract the data on this webpage page for use in other analysis tools (such as Microsoft Excel or a database). While some coders have written scripts to scrape this web page data, the script value is typically short-lived as it breaks whenever Weather Underground decides to change their page layout. Also, if you try to run too many queries too quickly via a script, some people have reported having their IP address blocked from accessing Weather Underground’s pages entirely. (Note that Weather Underground previously had a reasonably priced API to access this data, but that has since been abandoned in favor of a much more costly (more than $10,000 per year as of this writing) option that is out of reach for many.)

Another odd negative is that Weather Underground will often default to showing data from small, semi-private (schools, etc.) weather stations even when data is requested for larger towns and cities. These small stations can be far less reliable then major government-run stations at places like airports. People have reported finding examples of bad and missing data as well as weather stations that are reporting in the completely wrong location. To avoid this case, you will typically want to make sure that the selected station is a major one, and, if not, change it via the station picker option.

Single Location and Single Date

If you need access to a solution that can handle multiple locations and multiple dates, then a more robust option such as Visual Crossing Weather is likely the best for you. It is available in various forms including a Microsoft Excel add-in, a standalone web page, and a web services API.

To use the Microsoft Excel add-in for Excel version 2016 or later simply install it from the Microsoft App Source here for free. See our Weather Data products for more information. Once installed, the add-in will allow you to directly import weather data for any locations and dates in your Excel sheets. Select the location and date data in your sheet, and the Weather add-in will populate the appropriate weather metrics to match. Two of those weather metrics are precipitation and precipitation coverage and will give you the rainfall information that you seek.

Multiple Location Weather Using Microsoft Excel
Multiple Location Weather Using Microsoft Excel

Some of the positives of this approach are that you can easily get data get data for many locations and many dates very quickly. The add-in will automatically join in the appropriate weather data to match the dates, times, and locations contained in you Excel sheet. This is by far the fastest and easiest way to get weather data joined into Excel.

Another positive is that the Visual Crossing Weather tool relies on government weather reporting stations and will automatically interpolate among multiple stations in order to find the most valid weather details for a given location and time. This means that you don’t need to worry about selecting a “major” reporting station or manually account for situations where a specific station does not report valid data. The tool will automatically handle these cases without your intervention. You can read more about how we process integrated surface database historical weather data.

The primary negative is that you need to use Excel 2016 or later in order to be able to install the add-in. However, if you are using an older version of Excel or need weather data in another tool such as Google Sheets or a database, then there is a web page option with similar functionality.

When you click on the Data Services option on the Visual Crossing Weather Data page , and you will be shown a web page weather query option. On that page you can enter your location and dates directly. As described above for the Excel add-in, the tool will automatically find the closest and most valid weather station results that match your request locations. You can then export the resultant weather data to a CSV or a URL that can be loaded into virtually any analysis application. There are even helpful videos on the page to show you how to load the data into your analysis application of choice.

Multiple Location Weather Using Visual Crossing Weather Data
Multiple Location Weather Using Visual Crossing Weather Data

In addition to having many of the benefits of the Excel add-in option, the web page option offers a few additional benefits of its own. The primary one is that it allows a way to look up any quantity of weather data and then import that data into the tool of your choice. It is very fast and efficient especially when you need multiple weather metrics for multiple locations and dates. In addition, you don’t need to write brittle web scraper scripts to export the data. The page allows you to get the data as a CSV file or a URL via a single click. This makes the data itself virtually universal for importing into any tool. Finally, there is even an API if you want to write code to do automatic loading and refreshing into your own application.

If you combine both the Excel add-in and the web page version of Visual Crossing Weather, perhaps the most important benefit it ease-of-use. You can get the data that you need quickly, easily, and often directly into your analysis tool. In the case of Excel, the data is inserted directly into your worksheet right alongside your business data. In the case of the web page, there are helpful videos to guide you in importing the output weather data into common tools. This immediate access can not only save you time but can also eliminate mistakes that happen when trying to manually insert and merge data.

Summary

You can find historical rainfall and other metrics from various sources. If you need data for only a single location and date, a site such as Weather Underground can be used to view historical weather data easily. However, if you have need data for multiple dates and locations, a more robust weather data source such as Visual Crossing Weather can get you the data that you need without the slowness and frustration of the more basic consumer web page options. In addition, if you need the weather data in an analysis tool such as Excel, Google Sheets, or a database, then Visual Crossing Weather is the far better option.