textproduct: Indianapolis

KEY MESSAGES

- Hot and humid condition expected with highs in the 90s and heat indices peaking at 105 to 110 degrees in the afternoons through Thursday

- Extreme Heat Warning in effect through Thursday evening

- Thunderstorm chances will increase Friday through the holiday weekend

DISCUSSION (Today through Monday)

Issued at 237 AM EDT Tue Jun 30 2026

Muggy early this morning as with the center of the upper ridge across the Ohio Valley. 06Z temperatures remained between 75 and 80 degrees with dewpoints well into the 70s.

A dangerous heat wave will continue for much of the rest of the week as deep ridging sets up over much of the eastern half of the country. The ridge will flatten by late week as the jet stream drifts back south into the area. Scattered convection largely prevalent on any waves rippling through the flow will increase for the holiday weekend as a result.

The primary focus will be on the heat and humidity with at least 4 or 5 consecutive days with highs in the 90s. Monday was day one with highs in the lower 90s and heat indices that peaked over 100 degrees. Expect warmer air temperatures and higher heat indices today through Thursday with the core of the ridge over the area as mid level heights peak at 596-598dm. Increased subsidence over the Ohio Valley will limit clouds and diurnal cu as well...especially today and Wednesday. Likely to see a slight increase in cu development Thursday as moisture pivots around the back side of the ridge and into the area...but it is shallow and should not have much impact on expected highs.

Low level thermals support low to mid 90s each of the next three days with dewpoints remaining in the 70s. Max heat indices of 105 to 110 degrees are possible each afternoon. Considering the intensity of the heat with the compounding nature of impacts over multiple days from the oppressive airmass have elected to upgrade the Heat Advisory to an Extreme Heat Warning through Thursday evening. An increase in outdoor activities in advance of the Independence Day weekend also factored into this decision to upgrade. An argument could be made to extend the warning into Friday even as temps and heat indices fall back slightly from levels expected through Thursday...but increasing uncertainty on convective potential beginning Friday precludes an expansion in time at this point.

The ridge will slowly flatten heading into the weekend as waves aloft drift further south into the lower Great Lakes and Ohio Valley. Moisture lifting around the back side of the ridge may be enough to generate more cu and perhaps isolated late afternoon and evening convection by Thursday. Convective coverage should steadily increase Friday into the weekend as the mid level heights begin to fall back. Locally intense slow moving storms producing damaging winds during the afternoon and evening will be a possibility within the moist and highly unstable airmass. There remains the possibility of one or more mesoscale convective systems impacting parts of the region by the weekend as well...and there is already CIPS analog support for this solution by Saturday and Sunday. Very warm and humid conditions will linger into early next week.

AVIATION (06Z TAF Issuance)

Issued at 1221 AM EDT Tue Jun 30 2026

Impacts:

- Patchy ground fog possible early this morning - Wind gusts may peak at 15-20kts at times this afternoon

Discussion:

VFR conditions are likely to prevail throughout the period.

Given the very moist airmass in place...brief visibility restrictions near daybreak cannot be ruled out at the outlying sites. This remains too low of a probability to mention in the TAFs. Light southerly flow through daybreak will veer to southwest this afternoon and increase to 10 to 15kts at times. A sporadic higher gust is possible this afternoon as well...especially at KLAF. Winds will diminish near sunset.

IND WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM EDT Thursday for INZ021-028>031- 035>049-051>057-060>065-067>072.