Indy 500 rain policy: Will it rain? Here's the latest 2024 race day forecast

UPDATE: Find the latest weather forecast here.

Three days before the Big Race, outlooks continue to call for poor weather. While forecasts show increasing chances of rain, IMS likely won't announce any race delays before Sunday.

Here's what's in the forecast for other Indy 500 events and the big race May 26 as of Thursday:

Get weather alerts: How to stay informed in case of severe weather during Indy 500 weekend

What will weather be like for the Indy 500?

The National Weather Service in Indianapolis has increased its prediction of rain to 80% for Sunday's running. Thunderstorms are likely throughout the day with wind gusts at 18 mph. Temperatures will be around 80 degrees.

The Weather Underground is predicting an even likelier chance of wet weather with a 90% probability of rain and thunderstorms with the potential for weather to turn severe. Winds will hit 20 mph with temperatures in the mid-70s.

AccuWeather has normally had the most conservative outlooks this week but has increased its forecast to a 94% chance of rain with an 86% chance of thunderstorms. Storms could be strong and gusty in the morning and could bring flooding downpours, hail, damaging wind gusts and tornadoes.

Everything Indy 500: IndyStar's full coverage for this year's race

Will the Indy 500 be delayed or postponed?

Regardless of grim weather outlooks, IMS President Doug Boles said he's 99.9% sure there will be no announcements about postponements or delays prior to Sunday.

The Indy 500 has had only three complete postponements due to rainy weather since 1915, according to the IMS website.

The last time rain interfered with the big race was in 2007, when drivers were only able to finish 166 laps after having to stop twice from the weather.

Drivers must finish at least 101 laps for the race to be official, according to a 2019 IndyStar article.

Any postponement, either full or partial, will be made up the next day.

Potential postponements: What's the latest on the Indy 500 blackout and will the race be delayed by weather?

What will weather be like for Carb Day?

Friday is Carb Day, and NWS Indy is giving it a 40% chance of rain and thunderstorms, mainly after 2 p.m. Skies will be mostly sunny with highs near 84 degrees.

The Weather Underground is forecasting a 23% chance of rains for Carb Day with mainly cloudy skies. A stray afternoon thunderstorm is possible and highs could reach 83 degrees.

AccuWeather's forecast puts the chances of rain at 86% with a couple of afternoon showers and a heavy thunderstorm. Temperatures will be in the mid-80s.

What will weather be like for Legends Day?

Legends Day is Saturday, and the NWS says there's a 30% chance of showers before 8 a.m. Skies will be mostly sunny, with a high near 83.

The Weather Underground is calling for times of patchy fog and some cloudy intervals. Chances of rain are around 24% with temperatures in the lower 80s.

AccuWeather has the rain forecast at 25% chance of precipitation with mostly sunny skies and temperatures in the mid-80s.

Race Day delays: Why they don't run the Indy 500 in the rain

Indy 500 weather history

IndyStar analyzed 20 years of historic data from Weather Underground for May 26, this year's Race Day.

Daily temperatures averaged in the high 60s and it rained only 5 days out of the last 20 since 2004. Precipitation totals on rainy days were light, with the highest on record at only one-tenth of an inch.

On previous race days not always falling on May 26, temperatures varied wildly from a high of 92 degrees in 1937 and a low at 37 degrees in 1947, according to the National Weather Service.

The most rain fell on May 30, 2004, when Race Day was inundated with nearly 4 inches of precipitation.

Nat Newell contributed to this report.

Karl Schneider is an IndyStar environment reporter. You can reach him at karl.schneider@indystar.com. Follow him on Twitter @karlstartswithk

IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.

This article originally appeared on Indianapolis Star: Indy 500 rain policy: Will it rain on race day? Forecast as of May 23