We're getting close to the height of summer heat for Central Maryland, so it's no surprise that forecasters are calling for highs near 90 degrees at BWI-Marshall Airport Tuesday and Wednesday.

The heat and strong sun are helping to stoke air pollution chemistry. Central Maryland is under another Code Orange air pollution alert Tuesday. The alert means air pollution levels may become unhealthy for sensitive groups, including children, the elderly, and people with respiratory or cardiac conditions. The effects can be minimized by avoiding strenuous outdoor activity.  

The average daily high temperature for Baltimore at this time of year is 87 degrees, one tick short of the 88 degrees that marks the maximum for the year. That's reached between the 16th and the 25th of July. After that, the daily norms begins to slip as the length of the day shortens and sun angles begin to decline.

There's a front stalled across the region this week, which explains the persistent, if slight, chance of showers and thunderstorms Tuesday through Thursday. After that, high pressure in the Great Lakes should give the system a shove from the northwest. That will bring in some drier air, but only slightly cooler, with weekend highs close to the seasonal averages. We'll take it. Great beach weekend ahead. Don't forget the sunblock.

By early next week, the highs will be pushing back into the low 90s. For Hot-in-Baltimore contestants, the year's tally of 90-plus days now stands at 12 through Monday. The lowest guess was 15 days, by BD. By this time last year, we had counted 22. The annual average is about 29 days.

(SUN PHOTO: Kim Hairston 2011)