As politicians whose fates often depend on wringing extra dollars from state government, legislators from Prince George's and Montgomery counties say the warmest news thus far in 1985 in this ice-cloaked city is the massive infusion of cash that Gov. Harry Hughes' proposed $7.5 billion budget promises for their jurisdictions.

Naturally, the governor's spending program for 1986 includes the big-ticket items of local interest: more than $45 million to help defray the cost of Metro bus routes and the transit authority's bonded indebtedness, as well as $15 million for subway construction, some of which already is earmarked for Prince George's.

But Hughes' budget includes money for a host of smaller local projects, ranging from a $44,000 grant for research into a cure for the Potomac Fever that has ravaged Montgomery's horse population to increases in government payments to the large number of welfare recipients in Prince George's and elsewhere in the state.

"There's a piece of the action for everybody," said Thomas B. Stone Jr., Montgomery's legislative lobbyist. Roy Hart, Stone's veteran counterpart in Prince George's, went even farther, calling the spending plan "a ho-hum budget of no surprises."

Hughes' budget did spark protests from community college officials in the two counties. They said that the roughly $4 million in new aid to those schools is insufficient to help them in a year when enrollments are expected to dip slightly.

Under Hughes' budget, Montgomery College -- which, with nearly 11,000 full-time students, is the state's largest -- could receive an extra $537,735 on top of its $10.8 million state grant. Prince George's Community College in Largo, which has about 20,000 full- and part-time students, would receive nearly $1 million in addition to its $8.7 million basic funding.

"The governor's recommended funding is not enough," said Del. Charles J. Ryan (D-Prince George's). Ryan, chairman of the county's House delegation, and spokesmen for the two community colleges said they will ask Hughes to seek supplemental funding for the colleges later this year.

For Montgomery, Hughes' budget includes several prized appropriations, including more than $1 million to launch the Center for Advanced Research in Biotechnology, a joint venture near I-270 between the county, the University of Maryland and the National Bureau of Standards. The budget also includes a $1.6 million subsidy for the county's Ride-On bus system and $1.5 million in retirement benefits for county librarians.

Hughes also set aside $75,000 to begin the design of new state police barracks in Montgomery. The facility is scheduled to be relocated from Rte. 28 in Rockville to Seven Locks and Montrose roads because of the planned widening of I-270. The governor also allocated $24,000 for Mary's House, a shelter for women, as well as money to upgrade commuter rail stations in Germantown, Gaithersburg and Barnesville.

Like their counterparts in Montgomery, officials in Prince George's say they have few major complaints about Hughes' operating budget for state government and have turned their attention instead to the governor's $210 million capital budget.

Hughes already has given Prince George's one plum: nearly $3 million for a series of improvements to Rosaryville State Park, including roads, parking, utilities and other improvements needed to open the park for public use.

However, the capital budget does not now include $2.5 million needed to launch construction of the Hyattsville Justice Center, a court complex that County Executive Parris N. Glendening and others say is crucial to the revitalization of the aging Rte. 1 corridor between the District line and College Park.

"It's an essential project," said Del. Richard A. Palumbo, a Democrat who lives in Hyattsville. "Our biggest obstacle is that we'll be competing with other jurisdictions for the same pot of money."

Still, Palumbo and Ryan said they were optimistic about securing bonding for the judicial center. "We'll take a few things away from the governor and put in some things we like," declared Ryan, an Appropriations Committee member.

Montgomery County legislators, meanwhile, said they will press hard to win some of the $40 million in road and school bonds recently requested by County Executive Charles W. Gilchrist.

Privately, officials say they have no chance of persuading the General Assembly to fund the county's entire request, but are confident of obtaining some funds to help pay for Montgomery's mammoth public construction program.