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While this fall and winter have provided needed rain and Sierra snow in California, time is running out for significant drought relief from this strong El Niño as we head into spring.

After an optimistically wet start to the rainy season in the Golden State, including the highest Sierra snowpack measured in five years in late January, February trended much drier, despite a record-tying El Niño. The good news is that the start of March may now trend wetter again thanks to a large-scale weather pattern change.

San Francisco is an example of how dry it was last month, picking up less than one-quarter of their average February rainfall, typically their third wettest month of the year. 

Tahoe City, California, in the central Sierra, barely managed just over a foot of snow - 13.5 inches to be exact - in February, virtually all during one storm on Feb. 18-19. 

According to the California Department of Water Resources, snowpack water content Feb. 29 ranged 74 to 90 percent of the late-February average in the Sierra.

To be sure, this is a much better scenario than last year at this time, when Tahoe City managed only 9 inches of snow the entire season-to-date, 10 feet below the average pace.

(FLASHBACK: April 2015 Sierra Snow Survey Bare)

Roughly one-third of California's drinking water comes from the Sierra snowpack, which after melting later in the spring and summer replenishes the state's reservoirs.

California's reservoirs are mainly running from one-third to three-quarters of average as of Feb. 24, with the exception of Lake Shasta (82 percent of average) and Folsom Lake (116 percent of average).

(FLASHBACK: Folsom Lake Hits Record Low)

Much of the state remains categorized in the worst category of drought, an exceptional drought, according to the latest Drought Monitor analysis, which has been in place in at least part of California since January 2014. 

So, how much drought relief can California expect this spring as this El Niño lingers?

Wet Season Winding Down

First, we need to examine what typically happens in any year, regardless of El Niño.

California's distinct wet and dry seasons make significant precipitation in the fall-through-spring "wet season" critical to quench any drought, let alone one of the worst multi-year droughts in state history.

About three-quarters of the season's rain and Sierra snow typically dampens California from fall through February.

Climatologically speaking, March can still be rather wet, though, with an average of over 31 inches of snow at Tahoe City, and roughly 3.25 inches of rain in San Francisco.

By April, however, precipitation drops to less than half of March's totals. Come May, the faucet is almost shut off for the season.

Therefore, March will be a crucial month to add as much snowpack in the Sierra and as much runoff to reservoirs as possible.

(OUTLOOKS: National Forecast | Weekly Planner)

Past Strong El Niño Springs: Not All Wet

What happened to El Niño? Shouldn't California have been soaked by now?

Even a strong El Niño is only one of several factors at play in the atmosphere over any given day, week, or season. Therefore, the widely held belief that all El Niños soak the Golden State is a myth.

(MORE: Is La Niña Next?)

But this was a record-tying El Niño. Does that offer any hope for a wet spring?

In five previous strong El Niños (classified according to California meteorologist, Jan Null) dating to 1958, only three March-May periods were generally wetter than average in California. These include the last two strong El Niño springs, 1998 and 1983. 

Two of those strong El Niño springs, however, were generally dry, particularly in 1966.

To show the variance in spring rainfall during those five previous strong El Niños, here was the March-May rainfall in downtown San Francisco:

March-May Rainfall (inches)

1958

14.57

1966

1.35

1973

2.73

1983

12.99

1998

8.59

As we've seen so far this fall and winter, there's no guarantee a strong El Niño will provide significant rain and mountain snow in California.

"Analog climatology, especially given the relatively small number previous cases, should not be interpreted as a reliable forecast tool," said California consulting meteorologist Jan Null.

Null and fellow native San Francisco meteorologist, Dr. John Monteverdi, have chronicled how the 2015-2016 El Niño differs from past strong events.

"In recent months, it has become increasingly important to focus on how this event is different and not just lump it in as another 'strong El Niño'," said Null.

In the meantime, Californians will continue to hope for a wet spring before playing the same drought-relief waiting game next fall and winter.

MORE ON WEATHER.COM: California Flooding Photos (Jan. 2016)