textproduct: Louisville

KEY MESSAGES

* Highs in the low to mid 90s continue Tuesday as heat builds this week. Chances for heat indices above 100 degrees are highest within the Heat Advisory Tuesday through Thursday, being near a 60- 90% chance of occurring.

* Major Heat Risk is expected from Tuesday through at least Thursday. Depending on possible lack of storms, Friday may be included in this as well.

* A deepening trough will try to push chances for storms into our area Friday evening and Sunday as well.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 344 AM EDT Tue Sep 1 2026

Heat Advisory is in effect today and will continue through at least Thursday and may need to be extended until Friday. Currently, the Heat Advisory includes all areas along and west of I-65 and locations along and north of I-64 up to Franklin County. It does not include Lexington or areas along and east of the I-75 corridor. Depending on how temperatures warm today, we may need to expand the Heat Advisory further to the east.

Our prolonged heat wave continues as the strong 594 upper ridge positions itself right over the Ohio Valley and the Commonwealth of KY. Highs have gradually increased over the last couple of days and we expect that trend to continue with highs into the mid to upper 90s today into the middle of the week. It's not out of the realm of possibility we could have a few locations by Wednesday, Thursday or even Friday hit 100. Dew points continue to be in the upper 60s to low 70s but the expectation remains, as it has been the past couple of days, that as we approach peak afternoon heating we will start to see dry air mixing which will help lower dew points into the mid 60s. Even with the mixing, as temperatures continue to gradually increase, heat index values will start to reach 100 degrees and could start to see more heat index values climb to near 105.

The other aspect of this heat advisory is the wet bulb globe temperature. Unlike heat index that only accounts for the moisture in the air and air temperatures in the shade, the wet bulb globe temperature or WBGT also factors in sun intensity. These values start to reach the upper 80s which means that working or exercising in direct sunlight will stress your body after 20 to 30 minutes. It is also possible that by Thursday and Friday we could see some locations get to 90 or above which lowers the time your body is stressed in direct sunlight to around 15 minutes.

Lows will also remain very warm each night with light winds and temperatures remaining in the 70s. It is likely some of our more urban areas could see lows each night now until Friday morning in the upper 70s to near 80. This is also factored into issuing the Heat Advisory. With dew points each night still in the low 70s to upper 60s and nearly calm winds, you get very little relief from the heat.

Take time to stay hydrated, taking frequent breaks should you be outdoors for prolonged periods of time. Check on your neighbor as well, especially if their A/C doesn't work well or if they have none. SCT cumulus will return, but skies should remain dry still.

LONG TERM /FRIDAY THROUGH MONDAY/

Issued at 344 AM EDT Tue Sep 1 2026

===== Friday - Weekend =====

Trend in forecast guidance has been slower on shifting the upper ridge back to the west as an upper trough deepens over eastern Canada. While the upper ridge is expected to weaken some by the end of the week, the ridge axis is expected to remain over the Ohio Valley on Friday. If this trend continues, it is not out of the question that that temperatures remain hot in the afternoon, current forecast is picking up on this slow transition with highs on Friday now remaining in the upper 90s and heat index values ranging from 102 to 107 or higher. While confidence is growing, it still remain on the lower side. This is due to where we could see a weak sfc boundary set up over the region for Friday and where potential convective complexes move through the Ohio Valley Friday afternoon into Friday night. This placement of the boundary and potential convective activity will play a role on how much clouds we could see as well as rain/storm chances.

By Saturday and heading into Sunday, the deepening upper trough and associated upper low will slowly work southward into New England and the Canadian Maritimes. This will allow the upper ridge to continue to retrograde further to the west and allow for slightly "cooler" air to advect in from the north-northeast. While we could be nearly 10 degrees cooler this weekend than Thursday and Friday, that still means we would have highs in the 90s and upper 80s. We will also see an increase in shower and storm chances for Saturday into Sunday as the aforementioned sfc boundary is expected to be somewhere over the area during this time. Due to the temporal and spatial difference in current guidance, confidence remains low on the finer details for this weekend.

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/

Issued at 113 PM EDT Tue Sep 1 2026

SCT cu field is developing across the region as we get into peak heating. VFR conditions will continue, and we'll see clouds diminish as the sun begins to set. VFR continues overnight with light winds and SKC.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 8 PM EDT /7 PM CDT/ Thursday for KYZ023>035-038-061-062-070>072. IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Thursday for INZ076>079-083-084-089>092.