Weather: Heat increases this week with temperatures expected to be the highest on Tuesday Highs near 90 degrees on Monday Tags: DETROIT – After starting the holiday weekend below normal, we’re well above that mark and getting hotter. Smokin’ Hot Our first 90-degree days of the year didn’t arrive until last week. Now we’re racking them up. Tuesday looks like the hottest of the forecast with air temperatures in the low 90s. And with tropical humidity levels, heat index readings will be in triple digits in many spots, especially the Metro Zone. Our airmass really won’t change until Thursday, so don’t expect an appreciably different feel to Wednesday. We may lose a couple degrees because of additional cloud cover, but it will still be steamy. Thursday starts a cooldown that will last into the weekend. Remember, our normal high temperature is now 84. These next three plus weeks are statistically the hottest for Detroit. Then at the end of the month, normal temperatures start decreasing.