Underneath trees, especially those leafed out, will have a dramatically temperated and humidified climate. In old growth Redwoods that can take 20f off the extreme highs and lows and have 30% greater humidity. Also, where you are under the tree will drastically vary the amount of nutrient rich runoff a plant there receives. The base and drip line are vastly moister than in between at the surface.

I added the bullet about shade induced snow staying in a spot later into the spring.  My theory (starting to test) is that fruit trees (or bushes) that tend to lose blossoms due to frosts may delay their bloom if their roots are still snow covered for an extra week or two.  I've heard that a golf course somewhere wanted some blossoms to line up with a PGA tour so they piled snow around the trees to delay their bloom.

A person has to be careful about determining microclimates based upon plant types because a lot of that has to do with soil types and soil amendments too. Plants have a certain ideal soil and major and minor mineral mixture, so when they are present, they thrive. I do not know what dandelions have as I do not grow for or against them, but do know that milkweed thrives where phosphorous is low. Smooth bedstraw thrives where the PH is extremely low, etc. But plants can indeed indicate microclimates too.

Sadly I live on a North facing hill which is where the prevailing wind comes from, it is always windy here. Great for a windmill, but not so great for alfalfa. In some of my more exposed fields, I can only plant my sward with 10% alfalfa mixtures, whereas in a smaller field almost surrounded by trees, I can plant the sward to 90% alfalfa. The reason is because the wind blows off the snow cover and alfalfa is prone to winter-kill this far north.

Generally snow cover is a good thing. Swales across vast stretches of open land help pack in snow, then melts and moves it slowly where the swale leads it as the sun shines.

Hills are nice because they are warmer. My father lives 517 feet north of my house and down over a hill, yet I can plant my garden 2 weeks earlier because there is a sort of frost line between my home and his where the temp dips on some nights, just due to elevation.

Pockets of warm and cool air exist all across a property. A great way to find the warmer and cooler spots is to just walk it when the temp is around 70 degrees (f), the preferred temperature of humans. As long as a person is not overly covered up with clothing (think T-shirt and shorts here) they should feel the subtle differences in temperature. A person has to walk slowly so they do not generate extra heat, but around 67 degrees they will start to feel chilled, and around 74 they will start to feel warm. By doing this several times, at different times throughout the day, a microclimate of the property can be ascertained.

Dandelions are a sign of acidic, compacted soil. They draw up calcium with their tap root from the subsoil and have 10x the Ca content of lettuce. This balances out the ph, which at acidic extremes a locks out calcium to other plants. Curly dock and plantain are a similar signs of acidity and compaction. I use all of them in compost teas.

My dandies seem happiest near my French drain run off swales. Lots of water and nutrients from the ducks and composting woody debris basins/swales the water runs through on its way down hill. But that seems to help a lot of plants, which is why we designed it that way. It’s also good to remember many plants look like dandelions at a glance.

It may be a bit of a tangent from microclimates but plant soil indicators I know of include:
Dandelion/dock/plantain= acidic, compacted, wet
Buttercups = waterlogged soil
Wild lupines = nitrogen poor
Mints = wet soil

I don’t know sandy soil weeds as well because I work with mostly clay in my area.

I have huge granite cliffs overlooking meadows that have springs scattered up the valley. The hills/mountains around can be high desert.  I live at 8,500 ft and temperatures can drop to 30 or 40 below in some winters.  Almost anything I grow, other than the native aspens and evergreens, is pushing the zone.  USDA says it is zone 4, HA!  It is 2 or 3 unless we have a mild winter. I have the best luck with plants that grow in other areas that also have really cold winters, but different moisture levels.  I also have to have a hoop house or season extender to get produce from my garden.  Being very selective on the plants I consider helps.  I.e., some of the Canadian roses will do well here, few of the others will make it.