As someone who is extremely sensitive to temperature changes, likes to be prepared for whatever conditions are present, and spends a lot of time outside, I (obsessively) check the weather at least 3 or 4 times a day. I have various weather apps and websites I like to use depending on what I'm doing that day.
For example, one of my hobbies is fossil hunting! There are areas in Maryland and Virginia along the Potomac River and Chesapeake Bay where one can find millions-of-years-old fossils and sharks teeth literally just walking up and down a beach. Before going out for a hunt I like to check Willy Weather. This site is perfect to check before going out to do any activities on the water as it provides atypical information such as low & high tide times, swells, and moon phases, as well as your typical weather information like temperature, wind, rain, etc. While this site/app does provide great general weather information, I'm a little picky when it comes to presentation of information and I don't really like how their temperature forecasts are displayed. I mainly use this resource when I need to check tide times.
My go-to app for checking weather before doing more typical outdoor activities, like going for a bike ride or a hike at Banshee Reeks [;)] is the WeatherBug app (they also have a nice website - shown here - but the app is great if you're on-the-go!). I like WeatherBug because they provide a lot more information than your standard iPhone weather, such as dew point, pressure, UV index, air quality, and pollen counts. The hourly forecasts tend to be pretty accurate, and the additional information is helpful if the user wants to make predictions about future conditions on their own.
I should probably backtrack a bit and define what weather actually is. Weather describes the state of the atmosphere at a place and time in regards heat, dryness, sunshine, wind, rain, etc. In other words, it describes conditions as they are on a day-to-day basis. Climate, on the other hand, describes the weather conditions prevailing in an area in general or over a long period of time. It looks more at long-term historical trends of an area rather than day-to-day variances.
When it comes to finding climate information on an area, we have many resources at our disposal. My favorite that I've come across so far is provided by NOAA (National Oceanic and Atmospheric Administration) and can be access here. I like this resource because it provides a lot of information all in one place. You can observe monthly data reports compiled using long-term climate data including monthly temperature and precipitation spanning several decades (or monthly if you're interested in more recent information), as well as projections and outlook data surrounding temperature, precipitation, and severe weather. The screenshot I've provided above details average monthly temperature from December 2000. You can choose which month/year to look at, and some data sets allow you to set a date range to see conditions over years rather than months. This type of information may be useful when planning for a trip a little ways out - let's say you have some friends coming into town for a couple days in about a month and you want to take them on a hike around Banshee Reeks. Taking a look at monthly temperature and precipitation trends for the current month in past years and checking projections and outlooks for future conditions, as well as adding information from your daily weather apps, you should be able to predict what kinds of conditions you'll be facing on your hike.