I'll assume you haven't change your exhaust or water manifolds and you never had this problem before. There's a chance the intake gasket leaked at the water port, but most of the time water goes in the crankcase instead of #1 cylinder. There is also a chance that the cylinder pin holed over the winter. The way to check that is to use a leak tester with rocker arms removed on #1 so that both valves are closed. Put the piston a BDC and leak it. If your losing a bunch more air leaking the cylinder at the bottom rather than the top, or you notice pressure in your water system, you probably have a pin hole. This is just some checks you can do as your chasing the problem. You can also leak cylinder #1 with valves closed and remove rockers for cylinder #3 and the spark plug. Put air to the #1 cylinder and see if air is coming out #3 plug hole. That indicates head gasket not sealing between cylinders.