Data Collection and FAQs

Participate in Mountain Rain or Snow in three steps: 

Location: The web app needs your location to submit an observation, so make sure that your device’s location permissions are set to ON. 

Reach a member of the team: If you have questions, you can directly reply to your most recent text message from us (855-909-0798) at any time. 

Send observations while out of service: If you do not have cell service/wifi when you submit, the web app will save your observation for you to manually upload later. 

How often should we send observations?

Send observations whenever you notice that it has started to precipitate, or if you notice that the type of precipitation has changed. 

You can send observations as frequently as you remember while it is precipitating, down to 15 minute intervals. This is because the other variables that we use for data analysis that are matched to the time and location of the observation are tracked at fifteen minute intervals.

How do I recognize mixed precipitation? 

Mixed precipitation might look like slushy snow, or rain that is crystallizing.  As it falls, it might look part solid and part liquid. If it’s changing too fast to be sure, call it mixed.

If the precipitation is liquid as it falls, call it rain. If the precipitation is solid as it falls, call it snow (unless it’s hail or sleet - see below). 

Be sure to only report what is currently falling, rather than what is accumulating on the ground.

How should I classify graupel (snow pellets)?

Graupel is classified as snow for the purposes of this project. While there are many types of snow, we don’t need further specificity for the scope of Mountain Rain or Snow’s research question. 

Graupel and snow form by different processes high in the atmosphere, but the sets of conditions that both experience between the cloud and the ground fall into the “snow” category. Graupel looks like snow pellets. It has a softer texture than hail.

How should I classify hail and sleet? 

Do not send an observation if you see hail or sleet.  

Here’s why: hail, although solid, forms by a very different process than snow, and sleet, also solid, forms by yet another process altogether. The conditions that allow for either hail or sleet to fall are too complex to have a meaningful role in determining the rain-snow transition for the purposes of this project.

For fun, here’s how to tell the difference between hail and sleet. Hail consists of frozen balls of ice and falls at warm temperatures. Sleet also looks like frozen balls of ice, but it falls at cold temperatures. This page briefly discusses how hail and sleet form: Severe Weather 101: Hail Types (

Is freezing rain classified as mixed or rain? 

Freezing rain is liquid water that freezes when it hits the surface. 

Freezing rain is classified as rain in this project. We are concerned with the water’s journey through the atmosphere. The fact that it is a liquid while in the air is the key information for this project, even though it freezes when it hits the ground. 

For more information, visit this page on freezing rain and sleet

It’s precipitating very lightly. Should I still send an observation? 

Yes, send observations for very light precipitation. Even though only a small amount of precipitation is falling, this data helps build the model for whether or not snow or rain will fall in those conditions. 

Why don’t you want observations on the intensity of the precipitation? 

Mountain Rain or Snow doesn’t ask about the intensity of the precipitation because we don’t need to know how hard it is precipitating (or for how long) in order to figure out the point when falling snow turns to rain. We simply need to know if the precipitation has reached the ground as solid, liquid, or mixed in order to build a model for the behavior of precipitation in the near-freezing temperature range. 

How can I reach a real person with questions about the app or how to use the technology? 

You can talk to a real person that works on the Mountain Rain or Snow project by texting your question to 855-909-0798. (This is the same phone number we use to send out reminders.) We can respond to any questions that you send to this phone number. We’ll do our best to respond within 24-48 hours. 

Why don’t you have a field for me to enter the temperature?  

We don’t have a field for observations of temperature because the project uses temperature values from existing meteorological models to match your observations to the modeled temperature at your location. The scientific community has high confidence in modeled temperature data. 

Also, Mountain Rain or Snow is trying to improve the accuracy of rain-snow models which already use modeled temperature - we just need to know if, for the value the models use, they’re predicting snow versus rain correctly. 

For more information, check out “Quality Assurance and Quality Control” in the Methods section of this publication about Mountain Rain or Snow from 2021: Frontiers | Enhancing Engagement of Citizen Scientists to Monitor Precipitation Phase (

Why don’t you have a field for me to enter precipitation that fell in the past? 

There isn’t an option to submit an observation of precipitation in the past because there is no way to make sure that the time and location are completely accurate. For each observation that is submitted, a lot of information from meteorological models and measurements (from satellites, nearby weather stations, etc.) is matched up to the observation’s exact time and location. So, we need to make sure it is precipitating in real-time when you send the observation. 

For more information, check out the “Quality Assurance and Quality Control” section of the Methods in this article published about Mountain Rain or Snow from previous seasons: Frontiers | Enhancing Engagement of Citizen Scientists to Monitor Precipitation Phase (

When do you send text message weather alerts?

We send out text alerts for forecasted storms between November and May, because this is when the temperature outside is most likely to be in the range of interest for this project (about 28°F to 50°F). However, you can send observations any time of the year - you aren’t required to wait for a text alert from us to send an observation.

Should I send observations of rain/snow/mixed even if you didn’t send an alert? 

Whether or not we have sent out a text alert, if you make an observation, send it! We send alerts as reminders before storms that are forecasted to be in the temperature range of rain vs. snow uncertainty. Sometimes we miss a storm, or the forecast might be wrong, which is another reason why having observers like you ground-truthing observations is so important.

Why do you have only three categories of precipitation phase? 

We only give three options (rain, snow, or a wintry mix) because these three options tell us everything we need to know to answer this particular research question about the processes happening in the atmosphere. The forecast algorithms that we are trying to improve (used by NASA Global Precipitation Monitoring satellites) report a computed probability of the precipitation being liquid. Whether or not it is liquid is the information needed from community observers.

If you’d like to know more about how the satellites that we are trying to improve classify precipitation, check out the third FAQ on this page from NASA: IMERG: Integrated Multi-satellitE Retrievals for GPM | NASA Global Precipitation Measurement Mission

How often should I report if the conditions continue as the same type, like snow, for hours? 

It is helpful to receive repeated observations for the same precipitation type at consistent intervals. For example, submit an observation of an unchanged phase  at whatever interval you can manage (they do not need to be any more than every 15 minutes). Even one observation during the entire storm is very helpful! 

Should I report when precipitation stops?

There is no need to report when precipitation stops. But if it changes to a different type, submit that! This is because the main goal of the project is to help us to differentiate between solid/liquid/mixed precipitation. 

How can I indicate that the precipitation transitioned from one phase to another? 

If the precipitation phase changes, just submit a new report as soon as you notice the change. This helps us figure out what temperature the rain-snow transition occurs for your location. 

Up to what temperatures do you want observations? 

Submit observations any time it is precipitating. 

We are most interested in observations in the the temperature range with the greatest uncertainty for rain and snow, which is between about 28° to 50°F (-2°to 10°C). In this range, models have the hardest time accurately predicting rain vs. snow. However, we don’t remove any observations simply based on the temperature, so feel free to submit observations at any time that it is precipitating.

What is the ‘season’ for sending observations?

Send observations at any time of year. 

The temperature range of most interest for this project tends to occur between November and May, so we only send out text alerts during these months. However, you can submit observations at any time of the year, and they will still be included in the analysis. Storms near freezing can happen outside of November to May, so feel free to send observations at any time of the year.

Do you only want observations when I am in the mountains? 

Send observations at any altitude! The project focuses on mountainous regions because that is where rain vs. snow models struggle the most, but it is important for us to receive observations from a wide range of altitudes to verify that our models are correct. 

Also, the temperature of the rain-snow transition changes a lot based on where you are in the world and your altitude, so receiving observations from non-mountainous locations as well helps us to better predict precipitation phase for a range of locations.

Challenges with iPhone location: There are two places that you need to enable location permissions.  

1) In your general phone settings, open Privacy, then Location Services. Make sure the toggle at the top is on. Below this is a list of apps. Scroll through these apps until you find Safari (it may be listed as “Safari Websites”) then open it and allow location access. You can choose “Ask Next Time”, “While Using the App”, or “Always”, according to your preference.

2) Open the Safari app, then go to At the top of the page, click on the “AA” symbol. Open website settings from this menu, then allow location for the website (“ask” will also work).

Precipitation phase classification guide

If you need help determining if it is rain, snow, or mixed precipitation, check out this guide: