Photos by KYLE GREEN The Roanoke Times

On Tuesday, water cascades over the dam at Carvin's Cove, which is at full pond. The reservoir is one of two used by Roanoke and Roanoke County.

Carvin's Cove, benefiting from early-spring moisture, is full for the first time since May 2007.

Kevin Myatt is The Roanoke Times' weather columnist.

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The past few days' spell of July-like hot, dry weather serves as a reminder that all our early-spring moisture gains could easily be reversed if this kind of pattern gets stuck for weeks in the coming summer.

The good news, though, is that the two reservoirs from which the city of Roanoke and Roanoke County draw most of their water -- Carvins Cove and Spring Hollow Reservoir -- are full.

Carvins Cove, full for the first time since May 2007, was 8 feet below full pond in late February. Spring Hollow was more than 40 feet below full pond then.

The refill happened in spite of the fact that Roanoke is still nearly 3 inches below normal rainfall for the year to date, largely a result of the first two months having sparse rain and no measurable snow. Rainfall over the previous four years has totaled about 2½ feet below normal.

March, despite an early month snowfall and two other five-day rainy periods, actually finished about a third of an inch below normal at 3.47 inches.

Even April, with its regularly spaced rains the first three weeks, has slipped very slightly below normal rainfall to date during the recent dry period, sitting at 3.20 inches through Tuesday. A return to showery weather today and Thursday may lift April to near or slightly above its normal 3.61 inches.

What the past two months have shown is that regular, moderate rains at the right time of year can help fill reservoirs as well as or better than large but rare outbursts of torrential rainfall. Early spring is a good "recharge season" as rain can run into reservoirs and underground aquifers because tree roots aren't drawing out a lot of moisture just yet.

What the past few days have shown, though, is that if persistent high pressure sets up over the Southeast U.S., parching heat can occur as storm systems are diverted away from the region. This time it was only about five days. In summer, with the resisting force of the jet stream retreated to Canada, it can be five weeks, or more.

This hot, dry pattern breaks today. In fact, the same strong high pressure that brought the unseasonably hot weather will help bring showers and thunderstorms, as it causes a cold front to stall near us for several days and helps sweep Gulf of Mexico moisture northward along that front.

A stronger cold front will push through by the weekend, and we might even get back into somewhat below normal temperatures by next week.

Though it's felt like it the past few days, summer is still two months away. It's good knowing that the Roanoke Valley's water sources are full.