This report describes the historical weather record at the Louisville International Airport (Louisville, Kentucky, United States) during 1998. This station has records back to January 1948.
Louisville, Kentucky has a warm humid temperate climate with hot summers and no dry season. The area within 25 mi of this station is covered by forests (76%), croplands (14%), and built-up areas (8%)
Daylight saving time (DST) was observed at Louisville, Kentucky during 1998. There were two time changes during 1998:
1998 was not a leap year, so it has 365 days and no February 29th. The first leap year before 1998 was 1996 and the first after was 2000.
The summer and winter solstices and the spring and fall equinoxes mark the passing of the seasons. They fall on nearly the same day each year, with differences of a day or two depending on the year. In 1998 they occurred on:
|Spring Equinox||Friday, 20 March 1998.|
|Summer Solstice||Sunday, 21 June 1998.|
|Fall Equinox||Wednesday, 23 September 1998.|
|Winter Solstice||Tuesday, 22 December 1998.|
The hottest day of 1998 was September 6, with a high temperature of 97°F. For reference, on that day the average high temperature is 83°F and the high temperature exceeds 91°F only one day in ten. The hottest month of 1998 was August with an average daily high temperature of 87°F.
Relative to the average, the hottest day was December 6. The high temperature that day was 73°F, compared to the average of 48°F, a difference of 25°F. In relative terms the warmest month was January, with an average high temperature of 48°F, compared to an typical value of 41°F.
The longest warm spell was from November 22 to December 10, constituting 19 consecutive days with warmer than average high temperatures. The month of September had the largest fraction of warmer than average days with 83% days with higher than average high temperatures.
The coldest day of 1998 was March 12, with a low temperature of 13°F. For reference, on that day the average low temperature is 37°F and the low temperature drops below 26°F only one day in ten. The coldest month of 1998 was December with an average daily low temperature of 35°F.
Relative to the average, the coldest day was March 12. The low temperature that day was 13°F, compared to the average of 37°F, a difference of 24°F. In relative terms the coldest month was April, with an average low temperature of 48°F, compared to an typical value of 48°F.
The longest cold spell was from March 9 to March 17, constituting 9 consecutive days with cooler than average low temperatures. The month of March had the largest fraction of cooler than average days with 55% days with lower than average low temperatures.
The clearest month of 1998 was September, with 50% of days being more clear than cloudy. The longest spell of clear weather was from August 19 to August 29, constituting 11 consecutive days that were clearer than they were cloudy.
The cloudiest month of 1998 was January, with 90% of days being more cloudy than clear. The longest spell of cloudy weather was from January 2 to January 28, constituting 27 consecutive days that were cloudier than they were clear.
This station reports both the quantity of liquid precipitation and categorical observations of precipitation (e.g., moderate rain, or heavy snow). Both are subject to erroneous reports, but the former is particularly prone to false reports, especially ones indicating an excessive quantity of precipitation. Please bear this in mind when reading the extrema reported in this section.
The day with the largest quantity of precipitation was April 16. That day saw 1.850" of liquid (or liquid equivalent) precipitation, compared to a median value of 0.190". The month with the most precipitation was April, with 6.693", compared to a median value of 3.553".
As determined by quantitative measurements, the longest dry spell was from August 30 to September 17, constituting 19 consecutive days with no measured precipitation. The month with the largest fraction of dry days was October, with 84% of days reporting no measured precipitation at all.
The month with the largest fraction of days with at least some measured precipitation was April, with 57% of days reporting some measured precipitation.
This station reports when significant weather events (including precipitation) are visually observed at or near the station. Such events do not always correspond to measured quantities of liquid equivalent precipitation, such as when the event is near by not at the station, or in the case of solid precipitation that does not melt in the collection basin.
The day in 1998 with the most precipitation observations was February 5. There were 24 hourly weather reports that day (out of a maximum of 24) in which some form of precipitation was observated at or near the station. The month with the most precipitation observations was February, with 137 hourly present weather reports involving some form of precipitation.
As determined by the present weather reports, the longest dry spell was from August 30 to September 17, constituting 19 consecutive days with no observed precipitation. The month with the largest fraction of days without observed precipitation was October, with 84% of days reporting no observed precipitation at all.
The month with the largest fraction of days with at least some observed precipitation was April, with 70% of days reporting some observed precipitation.
In this section we consider only those weather reports that indicate liquid precipitation. For the purposes of this analysis, we include thunderstorms even though some thunderstorms are not accompanied by liquid precipitation.
The month of 1998 with the largest number of those reports was April, with a total of 119 reports. The day with the largest number of those reports was March 20, with a total of 17 reports.
This station reports when snow is observed falling but does not report the quantity of snow that has fallen or the depth of snow on the ground.
In this section we consider hourly weather reports that contain an observation of falling snow. These reports do not necessarily correspond to accumulation.
The first reported snow fall in 1998 was on December 22; the last was on March 21. The month of 1998 with the largest number of those reports was February, with a total of 69 reports. The day with the largest number of those reports was February 5, with a total of 24 reports.
Humidity is an important factor in determining how weather conditions feel to a person experiencing them. Hot and humid days feel even hotter than hot and dry days because the high level of water content in humid air discourages the evaporation of sweat from a person's skin.
When reading the graph below, keep in mind that the hottest part of the day tends to be the least humid, so the daily low (brown) traces are more relevant for understanding daytime comfort than the daily high (blue) traces, which typically occur during the night. Applying that observation, the least humid month of 1998 was September with an average daily low humidity of 40%, and the most humid month was January with an average daily low humidity of 66%.
But it is important to keep in mind that humidity does not tell the whole picture and the dew point is often a better measure of how comfortable a person will find a given set of weather conditions. Please see the next section for continued discussion of this point.
Dew point is the temperature below which water vapor will condense into liquid water. It is therefore also related to the rate of evaporation of liquid water. Since the evaporation of sweat is an important cooling mechanism for the human body, the dew point is an important measurement for understanding how dry, comfortable, or humid a given set of weather conditions will feel.
Generally speaking, dew points below 50°F will feel a bit dry to some people, but comfortable to people accustomed to dry conditions; dew points from 50°F to 68°F are fairly comfortable to most people, and dew points above 68°F are increasingly uncomfortable, becoming oppressive around 77°F.
To take some examples, and basing our categorization on the daily high dew point in 1998, January had 24 dry days, 7 comfortable days, and no humid days; April had 14 dry days, 16 comfortable days, and no humid days; July had no dry days, 4 comfortable days, and 27 humid days; and October had 5 dry days, 21 comfortable days, and 5 humid days.
The highest sustained wind speed was 39 mph, occurring on June 12; the highest daily mean wind speed was 21 mph (March 28); and the highest wind gust speed was 60 mph (June 10).
The windiest month was March, with an average wind speed of 11 mph. The least windy month was September, with an average wind speed of 6 mph.
Visibility is the maximum distance at which a given reference object or light can be clearly discerned. In the United States, visibilities that are greater than or equal to 10 miles are typically reported as 10 miles.
The day of 1998 with the lowest average visibility was February 6, with an average visibility of 1.5 mi. The month with the lowest average visibility was August, with an average visibility of 6.7 mi. With an average visibility of 8.8 mi, the month of November had the highest average visibility.
The cloud ceiling is the altitude of the lowest layer of clouds that are at categorized as broken (mostly cloudy) or overcast (cloudy). If no such cloud layer exists then the ceiling is unlimited and no value is reported.
The day of 1998 with the lowest average cloud ceiling was October 4, with an average cloud ceiling of 787'. The month with the lowest average cloud ceiling was January, with an average cloud ceiling of 5651'. The month of May has the highest average cloud ceiling, with an average cloud ceiling of 15000'.