Delaware Climate Data Definitions
Temperature Indicators:
Temperature -
- Ta (Average Temperature) - The average temperature value in a given time period (daily, seasonal, or annual). This is calculated by taking the sum of the maximum and minimum temperature values for the given time period and dividing that value by 2.
- Tn (Minimum Temperature) - The lowest temperature value in a given time period (daily, seasonal, or annual), usually occurring at night.
- Trg (Temperature Range (max -min)) - The range between highest and lowest temperature values in a given period (daily, seasonal, or annual).
- Tx (Maximum Temperature) - The highest temperature value in a given time period (daily, seasonal, or annual). The maximum temperature usually, but not always) occurs in the afternoon)
- TxSD (Standard Deviation of Max T) - The standard deviation of maximum temperature assesses the day-to-day variability in maximum temperatures.
- TnSD (Standard Deviation of Min T) -The standard deviation of minimum temperature assesses the day-to-day variability in minimum temperatures.
Temperature Extremes -
- days_20 (Days/Year Minimum Temperature<20F) - Number of days per year below the minimum temperature threshold of 20F.
- days_32 (Days/Year Minimum Temperature<32F) - Number of days per year below the minimum temperature threshold of 32F.
- days_90 (Days with Maximum Temperatures>90F) - Number of days per year above the maximum temperature threshold of 90F.
- days_95 (Days with Maximum Temperatures>95F) - Number of days per year above the maximum temperature threshold of 95F.
- days_100 (Days with Maximum Temperatures >100F) - Number of days per year above the maximum temperature threshold of 100F.
- days_105 (Days with Maximum Temperatures >105F) - Number of days per year above the maximum temperature threshold of 105F.
- days_110 (Days with Maximum Temperatures >110F) - Number of days per year above the maximum temperature threshold of 110F.
- nights_80 (Nights with Minimum Temperatures>80F) - Number of nights per year above the minimum temperature threshold of 80F.
- nights_85 (Nights with Minimum Temperatures>85F) - Number of nights per year above the minimum temperature threshold of 85F.
- nights_90 (Nights with Minimum Temperatures>90F) - Number of nights per year above the minimum temperature threshold of 90F.
- 4day_heatwave (Number of 4+ Day Heat Waves per Year) - Count of the number of extreme heat wave events per year. An extreme heat wave is a period of prolonged, unusual heat that lasts four or more consecutive days during which average temperatures exceed the historical 1-in-10 year events.
- maxdays_90 (Longest Period of Days with Maximum Temperatures>90F) - Longest consecutive days where the maximum temperature is above 90F.
- maxdays_95 (Longest Period of Days with Maximum Temperatures>95F) - Longest consecutive days where the maximum temperature is above 95F.
- maxdays_100 (Longest Period of Days with Maximum Temperatures>100F) - Longest consecutive days where the maximum temperature is above 100F.
Growing Season -
- firstfallfrost (Date of First Frost in Fall) - Date of first frost or first occurrence of freezing temperatures (below 32F) in the fall, marking the end of the growing season.
- lastspringfrost (Date of Last Spring Frost) - Date of last frost or last occurrence of freezing temperatures (below 32F) in the spring, marking the beginning of the growing season.
- growingseasonlength (Growing Season Length) - The "frost-free" period between the last frost in spring and first frost in fall or winter, defined as the last and first time the nighttime minimum temperature falls below 32F.
Energy-Related Temperature Indicators -
- cdd (Mean Annual Cooling Degree-Days) - An indicator of energy demand for cooling. This represents demand for electricity needed for air conditioning to keep cool in the summer. Cooling Degree-days are typically calculated a the cumulative number of hrs per year above the given temperature threshold value of 65F.
- hdd (Mean Annual Heating Degree Days) - An indicator of energy demand for heating. This represents demand for natural gas or oil for space heating to keep warm in the winter. Heating Degree-days are typically calculated a the cumulative number of hrs per year below the given temperature threshold value of 65F.
Temperature Extreme Percentiles -
- Q1_Tn (Nights with Minimum Temperatures Q5_Tn (Nights with Minimum Temperatures Q95_Tx (Nights with Maximum Temperatures >Historic 1-in-20 Hottest (95th percentile)) - Number of nights per year that reach a warmer maximum temperature than the historical 1-in-20 hottest nights (95th percentile).
- Q99_Tx (Nights with Maximum Temperatures >Historic 1-in-100 Hottest (99th percentile)) - Number of nights per year that reach a warmer maximum temperature than the historical 1-in-100 hottest nights (99th percentile).
Precipitation Indicators:
- Annual-Seasonal Precipitation Indicators:
- Pr (Precipitation) - Includes rain and snow, typically recorded as cumulative amount over a given time period ranging from day to year, in inches.
- 3mPr (3-Month Precipitation Change) - Percent change in cumulative seasonal (3-month running average) precipitation.
- 6mPr (6-Month Precipitation Change) - Percent change in cumulative
- 6-month average precipitation.
- 12mPr (12-Month Precipitation Change) - Percent change in annual average precipitation.
- percentagerain (Percentage of Precipitation Falling as Rain vs snow) - The percentage of the precipitation that falls as rain vs. snow during the year.
- pr_intensity (Precipitation Intensity) - Total precipitation over a season or year, divided by the number of wet days (where wet days are defined as days with more than 0.01 inches of rain in 24 hours) that occurred in that same season or year. Higher values of precipitation intensity tend to suggest that, on average, precipitation may be heavier on any given wet days; lower values, that precipitation may be lighter on average.
- spi (Standard Precipitation Index) - Measurements of drought with negative values indicating dry (drought) conditions and positive values indicating wet conditions.
Dry Days:
- drydays_longest (Longest Dry Period of the Year) - Longest consecutive days with no (or trace) precipitation (falling as either rain or snow).
- drydays_tot (Total Dry Days Per Year (precip<0.01 inches)) - The number of days per year with no (or trace) precipitation (falling as either rain or snow).
Extreme Precipitation:
- days_05in (Days per Year > 0.5") - Number of days per year with more than 0.5 inches of precipitation in 24hrs.
- days_1in (Days per Year > 1") - Number of days per year with more than 1.0 inches of precipitation in 24hrs.
- days_2in (Days per Year >2") - Number of days per year with more than 2.0 inches of precipitation in 24hrs.
- days_3in (Days per Year >3") - Number of days per year with more than 3.0 inches of precipitation in 24hrs.
- days_4in (Days per Year >4") - Number of days per year with more than 4.0 inches of precipitation in 24hrs.
- days_5in (Days per Year >5") - Number of days per year with more than 5.0 inches of precipitation in 24hrs.
- days_6in (Days per Year >6") - Number of days per year with more than 6.0 inches of precipitation in 24hrs.
- days_7in (Days per Year >7") - Number of days per year with more than 7.0 inches of precipitation in 24hrs.
- days_8in (Days per Year >8") - Number of days per year with more than 8.0 inches of precipitation in 24hrs.
- hist_2d_exceedance (Days per Year> Historical 2-day Maximum) - Number of times per year the historical 2-day maximum precipitation amounts are exceeded.
- hist_4d_exceedance (Days per Year> Historical 4-day Maximum) - Number of times per year the historical 4-day maximum precipitation amounts are exceeded.
- hist_7d_exceedance (Days per Year> Historical 7-day Maximum) - Number of times per year the historical 7-day maximum precipitation amounts are exceeded.
- wettest_14d_10y (Wettest Two Weeks in Ten Years) - The total amount of precipitation falling in the wettest two weeks (14 consecutive days) of 10 years.
- wettest_14d_1y (Wettest Two Weeks/ Year) - The total amount of precipitation falling in the wettest two weeks (14 consecutive days) of the years.
- wettest_14d_2y (Wettest Two Weeks in Two Years) - The total amount of precipitation falling in the wettest two weeks (14 consecutive days) of 2 years.
- wettest_1d_10y (Wettestd 1 Day in Ten Years) - The total amount of precipitation that fell on the wettest day of 10 years.
- wettest_1d_1y (Wettest 1 Day /Year) - The total amount of precipitation that fell on the wettest day of the year.
- wettest_1d_2y (Wettest 1 Day in Two Years) - The total amount of precipitation that fell on the wettest day of 2 years.
- wettest_5d_10y (Wettest 5 Days in Ten Years) - The total amount of precipitation falling in the wettest five days of 10 years.
- wettest_5d_1y (Wettest 5 Days/ Year) - The total amount of precipitation falling in the wettest five days of the years.
- wettest_5d_2y (Wettest 5 Days in Two Years) - The total amount of precipitation falling in the wettest five days of 2 years.
Humidity and Hybrid Indices
- RH (Relative Humidity) - The percentage of water vapor actually present in the air compared to the greatest amount of water vapor the air could possibly hold at the same temperature.
- Td (Dewpoint Temperature) - The temperature to which the air must be cooled to condense the water vapor it contains into water.
Heat Indices:
- summerheatindex (Summer Heat Index) - The summer heat index is a measurement that combines temperature and humidity, which affects evaporation and cooling Sometimes referred to as the "apparent temp", the Heat Index is a measure of how hot it really feels to the human body.
- hotdrydays (Number of Hot Dry Days per Year) - Number of "hot dry" days with maximum temp over 90F without measurable rain.
- coldwetdays (Number of Cool Wet Days per Year) - Number of cool wet days with precipitation. "Cool wet" days is defined as the number of days with maximum temperatures below 65F and measurable precipitation.
