High temperatures are at least 10 degrees above average across Central Indiana today. That places us in the mid to upper 80s despite the calendar reading September 27th.
While the sunny sky has been a major player in warming us up today there have been two other important ingredients. The first has been dry air. Water vapor is an effective greenhouse gas, so when the air is dry it is much easier for the temperature to rise or fall. The second ingredient has been a strong southwesterly flow. This functions sort of like a highway, which has allowed the warmth to stream northward into the state.
We will stay mild as we head into the evening and overnight, but temperatures will still drop fairly quickly with the dry air and clear sky. Tuesday will begin in the low 60s with a comfortable feel in the air. There may be some patchy fog in the early morning as well. A quick warm up will ensue after the sunrises with lunchtime temps reaching the upper 70s and low 80s and afternoon highs back in the mid and upper 80s. The entire day should remain very sunny and dry with only a few clouds drifting by.
Wednesday will repeat in the mid 80s, though a weak cold front will pass through later in the day. Warmth will persist through the end of the work week, but a steady cool down will ensue following the front. Dry weather will carry us into the weekend as well with our next rain chance not coming until late Sunday.