Persistent trade winds and Tropical Depression Cosme brought a reprieve from Hawai'i's long dry spell for many windward and upslope areas, but most leeward spots remain bone dry, according to July rainfall totals compiled by the National Weather Service.

Cosme, which passed about 225 miles south of Hilo over July 20 and 21, had the biggest effect on the Big Island, said hydrologist Kevin Kodama of the National Weather Service in Honolulu. The storm drenched the island's east and southeast slopes, with Hakalau and Glenwood collecting nearly 7 inches of precipitation during the two-day event.

The weather system "was mostly for the Big Island. For us, it really wasn't much," Kodama said.

A week earlier, O'ahu benefitted from an unseasonal shear line, the southern trailing edge of a cold front, that enhanced trade-wind showers. Some rain gauges along windward slopes recorded 1- to 3-inch daily totals during the event, according to weather service data.

"Normally we don't see shear lines this time of year," Kodama said.

Still, many parts of the state continue to suffer from a rainfall deficit, and last week the U.S. Department of Agriculture declared a drought emergency for the entire state due to dry conditions that have persisted since late last year.

Mandatory 10 percent water restrictions remain in place in Upcountry Maui, and portions of the South Kohala and Hamakua Districts on the Big Island are under a 25 percent reduction.

On O'ahu, the low reservoir level in the Waimanalo Irrigation System means a continuation of the mandatory 20 percent cut in irrigation water use.

Parched areas shouldn't expect significant showers through the rest of the summer, Kodama said.

"Barring any other tropical systems coming through, we're pretty much basing the forecast on seasonal expectations, with leeward areas for the most part continuing to be dry. Windward areas should be OK," he said. "We do not expect any relief until October."

While gauges along the slopes of the Ko'olau Range recorded near- to above-normal rainfall, the island's Leeward Coast saw less than 15 percent of normal precipitation during July, the weather service reported.

A meager 0.05 inches of rain was measured at Honolulu Airport last month, marking the second-driest July on record. The driest July occurred in 1950, when 0.03 inch was recorded at the airport.

Just 12 miles away, the O'ahu Forest National Wildlife Refuge gauge recorded a little more than 19.5 inches last month, the second highest total in the state and 130 percent of its normal rainfall for July, the weather agency said.

The forest refuge has collected a little more than 99 inches of rain so far this year, which is 82 percent of its normal rainfall. Only Kaua'i's Mount Wai'ale'ale, one of the wettest spots on Earth, has recorded more rainfall, at 214.61 inches for the year, which is near its normal level.

Pu'u Kukui at the summit of the West Maui Mountains is generally considered the second-wettest spot in Hawai'i, behind Wai'ale'ale. But so far this year, the site has received nearly 95.5 inches of rain, just 41 percent of normal.

Elsewhere on Maui, most of the windward gauges recorded near- to above-normal rainfall last month.

On the Big Island, most of the South Hilo and Puna District rain gauges showed below-normal totals, despite Cosme. The exception was Glenwood, which recorded a Big Island-leading total of 11.12 inches, or 112 percent of normal. Glenwood has been the Big Island's wettest spot this year, with 86.15 inches of rain.

Several gauges on Kaua'i, especially along the east-facing slopes, recorded near- to above-normal rainfall during July, while gauges across the rest of the island posted totals ranging from 40 to 80 percent of normal, the National Weather Service said.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.