Climate Thresholds

Instructions & Examples

How to use the Climate Thresholds tool

Step 1: Select a Threshold
Choose a parameter, whether it's daily high temperature, minimum relative humidity, or precipitation amount, along with your threshold of interest. Other customizable options include the time period to search, which year type to aggregate results to, and specific months or seasons to filter by. After making your selections, click "Search". If there are any errors with your submission, you will be prompted to correct them. Otherwise, the Step 2 panel will load.

Step 2: Find a Station
Stations that have data available to complete your request will be displayed on the map. Click on a station to select it, and click the "View Results" button to continue.

Step 3: Explore Data
Results may take up to 30 seconds to load, depending on the parameter, station type, and time period requested. After the results have been retrieved, the Step 3 panel will include information about the selected station, statistics about days meeting your selected threshold, and exportable plots and charts.


When is the typical first fall day when temperatures drop below freezing in Raleigh?

  • Step 1
    • Parameter: Temperature
    • Statistic: Low (Daily Minimum)
    • Criteria: Less Than or Equal To
    • Threshold: 32°F
    • Period: Entire Period of Record
    • Year Type: Aggregate by Snow Year
    • Filter Type: None
  • Step 2
    • Click on a station near Raleigh, such as the Raleigh-Durham Airport (KRDU)
  • Step 3
    • Within the Statistics box, the Average First Day with a low temperature ≤ 32°F is November 1.

How often does it rain more than two inches on a single day in Fayetteville?

  • Step 1
    • Parameter: Precipitation
    • Criteria: Greater Than
    • Threshold: 2 in.
    • Period: Entire Period of Record
    • Year Type: Aggregate by Calendar Year
    • Filter Type: None
  • Step 2
    • Click on a station near Fayetteville, such as the Fayetteville Pwc COOP station (313017), which has data going back to 1871.
  • Step 3
    • The Statistics box shows there have been 295 days with more than 2 inches of precipitation observed in Fayetteville, or an average of 2.2 days per year (calculated using only years with at least 90% of data available).

What is the longest streak of summer days with a heat index reaching 100°F in New Bern over the past decade?

  • Step 1
    • Parameter: Heat Index
    • Statistic: High (Daily Maximum)
    • Criteria: Greater Than or Equal To
    • Threshold: 100°F
    • Period: Specific Date Range from Jan 1, 2010 to Dec 31, 2019
    • Year Type: Aggregate by Calendar Year
    • Filter Type: By Season, for the Summer (June, July, and August)
  • Step 2
    • Click on a station near New Bern, such as the Craven County Airport (KEWN).
  • Results
    • Under the Data Tables heading next to Streaks, click the "Show Table" button. The longest streak, listed first, is 13 consecutive days from Jul 11-23, 2019.

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Have you ever wondered when the first fall freeze usually happens? What about the number of days each summer with a high temperature above 90°F?

The Climate Thresholds Tool can answer these questions. It provides statistics, such as the average first and last dates and the total number of days a threshold is met, and data plots for a number of weather parameters.

To use this tool:
  • In Step 1, select a parameter, threshold, and other search details.
  • In Step 2, choose your weather station of interest from the map.
  • In Step 3, view charts and tables to easily visualize the results.
Step 1: Select a Threshold
Select your weather parameter of interest. Depending on which parameter you select, you may also be prompted to choose a statistic. For example, choosing "Temperature" with a statistic of "High" would search for daily maximum temperatures meeting the threshold you select below.

You must select a parameter.

You must select an aggregation type.

Select your threshold criteria and the threshold itself. If you choose the "Between" option, you will be prompted to enter two thresholds. The first one should be less than the second one.

You must select a threshold type.

You must enter a threshold value, as a number. For the "Between" option, the second threshold must be greater.

You must select inclusive (i.e., greater than or equal to) or exclusive (i.e., greater than).

You must select valid units for your parameter.

Time Period
Select the historical time period to search from each station. If you choose the "Entire Period of Record" option, note that different stations have varying availability, ranging from a few years to many decades. To view the same time period across multiple stations, choose the "Specific Date Range" option.

You must select a time period type

You must select a valid start and end date. Dates must be between Jan 1, 1850, and January 19, 2021.

Year Type
Your results will be grouped by year, but in some cases, you may not want them aggregated by Calendar Year. When searching for temperatures below a threshold of interest, you may want to search by Snow Year, which is centered on the winter season. This will ensure the first day below that threshold occurs in the fall, not in the spring. You can also search by Water Year, which may be useful for water resource statistics such as extreme precipitation occurrence.

You must choose a year type

Filter Dates
You may want to restrict your search to specific months or seasons, for example, to see the occurrence of high temperatures above 90°F only in the month of April, or only in the spring. Seasons are defined climatologically, so winter includes December, January, and February.
Filter Type:

Please select one or more months or seasons to use that filter.

Step 2: Find a Station
Step 3: Explore Data