It all started with a simple question from my wife: "What will the weather be like on our wedding day?" We were planning our wedding at Starved Rock State Park, and with the date set a year in advance, we were curious—and maybe a little nervous. Weather forecasts only cover about 10 days, and climate models focus on long-term trends, so how could we predict what to expect on our big day? Would it be sunny, snowy, or pouring rain? That question sparked my dive into historical weather data and eventually led me to create a tool to help others answer similar questions.
Luckily, my work with the Google BigQuery team had introduced me to a wealth of public datasets, and one in particular caught my eye: the NOAA Global Summary of the Day (GSOD) database. This treasure trove of information contains daily weather records from thousands of stations worldwide, tracking everything from temperature and rainfall to wind speed. It’s like a time machine for weather, letting you see what conditions were like on any given day in the past hundred years or so.
It's important to note that this project is a personal side endeavor, developed on my own time and hosted using my own resources. Any information shared here is my own work and doesn't necessarily reflect the views or endorsements of my employer.
I dove into the data, crafting a query to pull weather records from stations near our venue. After some analysis, I had a clear picture of what to expect. For our wedding date, the average high was 37°F (3°C), and the average low was 18°F (-8°C). But since weather can be unpredictable, I also looked at the range of likely outcomes: about half the time, the low temperature fell between 10°F (-12°C) and 27°F (-3°C). This helped us prepare for the possibility of a chilly—or even snowy—day.
Screenshot of an early version of overcastdata.com.
This data helped us make smart decisions, like choosing the right attire and preparing for the possibility of snow. And sure enough, our wedding day was a beautifully temperate--but still snowy--wonderland! After that, I started using the tool for all kinds of planning. For example, when my wife and I were packing for our honeymoon in Spain and France, historical weather data helped us decide what to bring. But for a while, it remained a personal tool.
I realized this could be helpful for a lot more people. Anyone planning an outdoor event, or simply curious about their local weather history, could benefit. That's why I teamed up with Mario Torres Jr., a former apprentice of mine from Google. He's been instrumental in helping me make this tool more accessible. You can find him on LinkedIn: https://www.linkedin.com/in/mario-torres-jr. Together, we're working to make it easier for everyone to explore their local weather history.
Curious about the weather history in your area? Whether you're planning a wedding, a vacation, or even a garden, Overcast Data can help. Visit overcastdata.com to explore historical weather patterns and make your plans with confidence. What surprises will you uncover? We’d love to hear how you use the tool—share your stories with us!